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Pragmatic Version Control

1. The Pragmatic Ogrammers Pragmatic ersion Control Using Git The Pragmatic Starter Kit Volume 1 Travis Swicegood Edited by Susannah Davidson Pfatzer Prepared exclusively for Frode Nilsen What readers are saying about Pragmatic Version Control Using Git Pragmatic Version Control Using Git is an excellent guide to getting you started with Git It will teach you not only how to get yourself started but also how to cooperate with others and how to keep your history clean Pieter de Bie Author GitX If you are thinking of using Git I highly recommend this book If you are not using a version control system and code or create content on a computer put the book down slap yourself pick the book back up and buy it Jacob Taylor Entrepreneur and Cofounder SugarCRM Inc Not only has this book convinced me that Git has something to offer over CVS and Subversion but it has also showed me how I can benefit from using it myself even if I m using it alone in a CVS Subversion environment I expect to be a full time Git user soon after reading this which is hard to believe considering this is the first distributed version control system I ve ever looked at Chuck Burgess 2008 PEAR Group Member Travis has done an excellent job taking a tricky subject and making it accessible useful and relevant You ll find distributed version control and Git much less mysterious after reading this book Mike Mas
2. After you ve saved your change run git status again prompt git status On branch master Changes to be committed use git reset HEAD lt file gt to unstage modified index htm Changed but not updated use git add lt file gt to update what will be committed modified index html dk dk dk dk dk Gk Gk Gk Now there s two index html files listed The first one is the change you staged earlier You can tell this because of that header Changes to be committed The second one is the change you just made It hasn t been staged yet so it has the Changed but not updated header above it The first will be green and the second red if you turned on color ui back in Section 2 2 Configuring Git on page 31 Report erratum Prepared exclusively for Frode Nilsen SEEING WHAT HAS CHANGED lt 4 60 You just made the changes so I m sure you still remember what they are Sometimes you need to see though To do that you can check the diffs the differences between the files Viewing Difference Git can show you the differences between what s in your working tree what s staged and ready to be committed and what s in your repository You use the git diff command to do this Calling git diff with no parameters shows you the changes in your work ing tree that you haven t staged or committed yet prompt git diff diff git a index html b index html index ca86894 5fdc539 100644 a index h
3. The next step is the license and any incompatibilities between the Win dows version of Git and the nix version Since this project is aimed at Windows there will always be slight differences such as how line 6 http code google com p msysgit Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 INSTALLING GIT Md 30 Git Setup Welcome to the Git Setup Wizard This will install Git 1 5 5 preview20080413 on your computer It is recommended that you close all other applications before continuing Click Next to continue or Cancel to exit Setup Figure 2 1 Welcome screen for Git installer endings are handled Don t worry about these changes Any deviations from the standard Git are there to make it run better on Windows The next two steps are the location to install Git in and the name of the folder you want Git to create in your Start menu The defaults are fine The next step is the additional enhancements you want Git on MSys to install Leaving these at the default settings is fine The next step as shown in Figure 2 2 on the following page adds Git to your PATH environment variable This is necessary for Windows to know where to find the git command on your system There are three choices You should choose the second option It allows you to invoke Git directly from the command line without adding any extra functionality Git on MSys starts the installation process
4. that is it has everything it needs to satisfy this release but hasn t been fully vetted yet This type of branch will have only minimal changes made to it and all will focus around fixes whether they are bugs or logic but no new features are added These release branches make it easy to continue developing new features on the master branch while the team has a copy of the code that is about to be released without the new code in it Release branches are normally prefixed with an RB_ and contain the number of the release So a version 1 2 release would be RB 1 2 while the 1 3 version would be RB 1 3 The release branch should last only for a short period while your release goes through any final testing Once the release is ready you create a tag to mark the occasion and delete the branch Don t worry about deleting the branch you don t have to keep a branch around to keep that history Your tag marks its place There s no need to keep a branch around cluttering up your branch list What about fixing the inevitable bug that pops up in a release You create a new release branch based on the tag like we did in the previous section Use the RB_ prefix and specify the tag you want to create it from prompt git branch RB 1 0 1 1 0 prompt git checkout RB 1 0 1 Switched to branch RB 1 0 1 Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 HANDLING RELEASE BRANCHES 4 113 All yo
5. title to index 7b1558c add in hello world HTML There s one final piece of the release puzzle that Git can help you with creating an archive of your release You don t always need to distribute the history of your project with your releases Often a tarball or zip file Report erratum red exclusively for Frode Nilsen HANDLING RELEASES lt 47 of it at the point you tag is enough Git provides the git archive command to do that This is how you create a gzipped tarball of mysite prompt gt git archive format tar prefix mysite 1 0 1 0 gzip gt mysite 1 0 tar gz There are three parameters here First format tells Git to generate tar output Second prefix tells Git to put everything in the mysite 1 0 directory Finally 1 0 tells Git to use that tag to determine what to store in the archive The third line gets a little more complicated if you re not used to Unix style commands It pipes the output from git archive a tar file to gzip which compresses the file The output is then sent to the mysite 1 0 tar gz file that you can distribute git archive also lets you create zip files Creating zip files is a little more straightforward because the output from git archive is already com pressed You can use the following command to create a zip file prompt gt git archive format zip prefix mysite 1 0 1 0 gt mysite 1 0 zip The parameters are almost the same between the zip and t
6. 2 2 Configuring Git Git requires a few pieces of information from you to work Since it is distributed there s no central repository to ask what your name or email address is You can tell Git this information by using the git config command To start with we ll configure a few global values These are the default configuration values used by every repository you create on your sys tem To set these configuration values as global add the global option The first two settings that must be set are username and user email The first is how you want your name to appear when you commit a change Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 20 CONFIGURING GIT lt 32 C WINDOWS system32 cmd exe Microsoft Windows XP C Copyright 1985 2661 Mi C Documents and Settings Travis gt git version git version 1 6 6 2 1172 ga5ed8 C Documents and Settings Travis gt Figure 2 3 Displaying the current version of Git in Windows and the second is an email address that other developers can use to contact you regarding your change Of course substitute your name for mine prompt gt git config global user name Travis Swicegood prompt gt git config global user email development domain51 com You can verify that Git stored your settings by passing git config the list parameter prompt gt git config global list user name Travis Swicegood user emai l development
7. 9 2 Exporting Your Repository On a successful project you have to release the software you re creat ing If the software is written in one of the modern scripting languages such as Python or Ruby or PHP you have to include the source for the end user to be able to run it You can do this by providing access to your public Git repositories but creating official releases that are snapshots of your project reduces the amount of knowledge needed for your user to get up and running with your software Git provides a convenient tool for creating such a snapshot git archive It exports your code in either tar or zip format creating an exact copy of your repository at the point you give it git archive takes a few parameters First you have to specify the for mat you want by specifying the format lt format type gt parameter Valid format types are tar and zip Second you must supply a point in the history of the repository you want to create the archive from This can be a commit a branch or a tag That s all you have to provide but another useful parameter is prefix Using that you can specify what you want the files that are exported to be prefixed with You can use this to put your release in a particular directory For example you can create an archive of the mysite repository you ve been working on Execute this command from within the working tree of your repository prompt git archive format zip N prefix my
8. Counting objects 41 done remote Compressing objects 100 35 35 done remote Total 41 delta 14 reused O delta 0 Receiving objects 100 41 41 4 52 KiB done Resolving deltas 100 14 14 done prompt gt cd mysite chp5 6 1 Inspecting Git s Log The commit log is the most common way for you to inspect what has happened to your repository Git shows each new commit s log entry along with who made the commit when and optionally the changes that were made It s displayed in a reverse chronological order like a blog You can pro vide all sorts of parameters to filter the log but let s start with the basics Just type git log at the command prompt from within your work ing tree prompt gt git log commit Obb3dfb752fa3c890ffc781fd6bd5dc5d34cd3be Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 11 06 47 2008 0500 add link to twitter commit 18f822eb1044761f59aebaf7739261042ae10392 Author Travis Swicegood developmentQdomain51 com Date Sat Oct 4 10 34 51 2008 0500 add contact page has primary and secondary email Git sends the log output through less if there is more than it can display on one screen That lets you scroll through the log You can tell that there s more output by the presence of the at the bottom of the screen Report erratum Prepared exclusively for Frode Nilsen SPECIFYING REVISION RANGES lt 82 The default output from git log shows you
9. Installation 30f 31f 26 31 32f Gitosis 147 149 Linux 27 28 Mac OS X 28 Windows 28 31 32f Interactive mode 54 K Keys 150 152 Komodo IDE 169 L Linux installation 27 28 Locking 24 Log messages 42 81 82 M Mac OS X CPAN 142 FileMerge Utility 77f installation 28 MacPorts 26 140 142 MacVim 63 169 Makefiles 26 Master branch 43 45 112 Merging 22 23 69 73 Milestones marking 110 112 Moving files 62 MSys 29 N Naming 110 114 115 Network protocols 101f 102f 100 103 nohup 155 OQ Online resources 13 Optimistic locking 24 Organization 19 20 Orphaned commits 129f l patch mode 54 Perl bindings 140 Port 9418 101 Practices of an Agile Developer Working in the Real World Subramaniam amp Hunt 141 Public key 150 152 Pulling 19 Pushing 17 19 105 106 145 Python 148 R Rebasing 45 Rebasing branches 125 128 reflog 129f 128 130 REGULAR EXPRESSIONS p VERSION CONTROL SYSTEMS VCSs Regular expressions 87 Release branches 43 45 112 114 Releases 45f 46f 44 47 116 Remote repositories 100 107 adding 106 107 cloning 103 104 commands for 164 fetching 104 105 network protocols 101f 102f 100 103 pushing changes 105 106 Remote repository see also Repository Renaming branches 78 79 Renaming files 62 repo or cz 171 Repository 16 17 adding files 52 56 bisecting 131f 132f 131 134 branche
10. M VCSCommand 169 VCSs see Version control systems Version control systems VCSs benefits of 10 branches 22f 21 22 configuration management 25 defined 15 file manipulation 18 19 history 80 99 blame 86 88 changes undoing 91 94 VERSIONS p WORKING TREES content tracking 88 91 log 81 82 reviews of 94 99 revision ranges 82 85 version differences 85 86 locking 24 merging 22 23 organizing 19 20 repository 16 17 37 tags 20 21 what to store in 17 working trees 18 see also Git Versions 85 86 155 Virtual machines VMs 106 Wo Windows installation 28 31 32f Working trees 18 Web 2 Welcome to the Web version 2 0 You need some help to tame the wild technologies out there Start with Prototype and script aculo us a book about two libraries that will make your JavaScript life much easier See how to reach the largest possible web audience with The Accessible Web Tired of getting swamped in the nitty gritty of cross browser Web 2 0 grade JavaScript Get back in the game with Prototype and script aculo us two extremely popular JavaScript libraries that make it Win eere a walk in the park Be it Ajax drag and drop igne o Cac ai autocompletion advanced visual effects or many other great features all you need is to write one or two lines of script that look so good they could almost pass for Ruby code Prototype and script aculo us You Never Knew JavaScript Could
11. March 2009 LOCKING OPTIONS 1 9 Locking Options When you go to the library to check out a book not this one because you bought a copy right no one else can check it out again until you turn it back in The reason for this is simple when the library has only one copy of the book it can t physically give it to more than one person at a time When a lot of people first hear the word check out and that it relates to version control they automatically think that version control must be like a library only one person making changes at a time Some VCSs do work like this You ask the repository if you can have the settings py file to make some changes It says yes and then prevents everyone else from making changes until you check it back in This is locking at work in particular it s strict locking Just like a library only one person can have a copy of the code at a time This isn t an efficient way for a team to work together though and doesn t fit with our DVCS model where everyone is only loosely connected to everyone else The alternative that most VCSs and all DVCSs use is called optimistic locking Optimistic locking allows multiple developers to work on the same code in the same files with the assumption that most of the time their changes won t conflict It works like this Joe and Alice both create clones of the repository they share and start making changes They both make changes to the same file but in diff
12. P2 0 printing March 2009 COMMITTING CHANGES lt q Tracking Em Directori Git doesn t track directories There has been some historical resistance to the idea of tracking empty directories The theory goes that most well maintained projects don t actually need empty directories That may change in the future and Git might track directories but in the meantime there is an easy workaround if you need to store an empty directory Just add an empty file in the directory you want to track and add it to your repository You can name the file anything you want but most people start the file s name with a period because most file systems ignore files that begin with a period The change is not sent to a central repository though Other people can pull the change from you or you can push the change to some other repository but there s no automatic updating We ll talk about these in Section 7 3 Keeping Up to Date on page 104 and Section 7 4 Pushing Changes on page 105 You can use git commit in multiple ways to commit changes to your repository but every commit requires a log message For simple mes sages you can add a message by adding m your message The message can be any valid string You can also specify multiple paragraphs by passing multiple m options to git commit For more complex messages that require an editor you can execute git commit without the m and Git launches your editor to create your log mess
13. other developers all push changes to Pushing is what you do when you want to send your data to another repository so it can be shared with other developers Pushing changes is just half of what you need to do to stay in sync You also have to fetch changes to get the latest updates from other members on your team There are two steps to retrieving changes from a remote Git repository First you fetch them That creates a copy of the remote repository s changes for you This step is sort of like the reverse of pushing Instead of sending changes to another repository you ask the remote repository to send you the changes it has Next you merge those changes into your local history Git provides tools that help you merge changes Since you normally want to fetch and merge changes at the same time Git provides a way to do both in one step through a process called pulling Pulling is similar to an update command in Subversion or CVS Git is fully distributed though You can push and pull changes to and from multiple repositories Working with remote repositories is a core part of fully understanding how Git works We ll cover it fully in Chap ter 7 Working with Remote Repositories on page 100 1 5 Tracking Projects Directories and Files So far you ve seen how to store your code in repositories In this section we ll talk about how to organize the things you store At the lowest level Git tracks the files you store in your reposit
14. 3899 reused 5680 delta 3505 Receiving objects 100 6318 6318 1 03 MiB done Resolving deltas 100 3899 3899 done From git ourcompany com dev erin git branch HEAD gt FETCH_HEAD Merge made by recursive a bunch of output showing the result of the pull Report erratum Prepared exclusively for Frode Nilsen ADDING NEW REMOTE REPOSITORIES lt 108 That s a lot easier to remember Of course erin is completely arbitrary You can name it whatever you would like The only limitation is that each name must be unique You can have only one erin or origin You can use git remote add to add an origin to your repository if you don t have one This is useful when you start a repository locally with git init and then need to send it to a remote repository later There are some other useful ways to use the git remote command too You can call it without any parameters to see a list of all the remote aliases you have created and git remote show name will show you some information on the remote repositories You can call git remote rm to remove a remote alias if you no longer need it or want to use that name for another repository That wraps up remote repositories and almost finishes up our tour of commands you need to know when using Git Report erratum Prepared exclusively for Frode Nilsen Chapter 8 Having the entire history of your project available to you is the key benefit to any version control s
15. 6 Cloning a Remote Repository 48 II Everyday Git 50 4 Adding and Committing Git Basics 51 Al Adding PES reos e sosis con eom Rm mcm Rm Re 52 4 2 Committing Changes 55 4 3 Seeing What Has Changed 2 048 05 58 4 4 ManagingFiles eee 61 5 Understanding and Using Branches 65 Sl WHarLAre Branches 6 2 ode or Boe ale wee 66 5 2 Creatinga New Branch ose spes s 67 5 3 Merging Changes Between Branches 69 5 4 Handling Conilets gt ss s e soss uos we 74 5 5 Deleting Branches 6 6646 eae or nn 77 5 6 Renaming Branches se cessera 5058 nh 78 6 Working with Git s History 80 61 Inspecting Gits Log uu seu Gh Re a a a 81 6 2 Specifying Revision Ranges 82 6 3 Looking at Differences Between Versions 85 6 4 Finding Out Who s to Blame 86 6 5 Following Content s ss s es srir se serea wes 88 6 6 Undoing Changes sss sese sa sii Re Ux 91 Of Rewri ng FHIStoy 2 G2994 944 999 94 7 Working with Remote Repositories 100 7 l Network Protocols 4 cse we n 100 7 2 Cloninga Remote Repository 103 7 3 Keeping Up to Date lens 104 7 4 Pushing Changes s 105 7 5 Adding New Remote Repositories 106 Report erratum Prepared exclusively for Frode Nilsen 2009 CONTENTS lt 7 8 Organizing Your Repository 109 8 1 Marking Milestones with Tags 110 8 2 Handlin
16. 88 Be careful though If you find yourself copying a lot of code around it might be a sign that your code needs to be refactored to avoid duplication Ignoring Files Depending on your editor you might be seeing slightly different output from git status Actually that s because I changed my repository and didn t tell you about it This is what my output looks like when I remove that change and run git status prompt git status On branch master Your branch is ahead of origin master by 2 commits L Untracked files use git add lt file gt index html swp nothing added to commit but untracked files present use git add to track to include in what will be committed My favorite editor is MacVim Whenever I start editing a file with it it creates an swp file for internal tracking That s cruft that doesn t need to be in the repository You can ignore it by adding it to the gitignore file and it disappears 1 Refactoring is the art of making code better by small incremental changes For a thorough introduction to the topic there is no better source than Martin Fowler s book Refactoring FBB 99 2 http code google com p macvim Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 MANAGING FILES Adding one file at a time to ignore is inefficient so Git allows wildcards Since I know that MacVim swap files always begin with a peri
17. 9776166 3 0 39 95 http pragprog com titles rails2 f You Need to Know Learn the best ways to use your own brain and the best ways to use Ubuntu Linux Either way this is stuff you need to know Pragmatic Thinking and Learnin Software development happens in your head Not in an editor IDE or design tool In this book by Pragmatic Programmer Andy Hunt you ll learn how our brains are wired and how to take advantage of your brain s architecture You ll master new tricks and tips to learn more faster and retain more of Refactor what you learn Your Wetware Use the Dreyfus Model of Skill Acquisition to become more expert Leverage the architecture of the brain to strengthen different thinking modes Avoid common known bugs in your mind Learn more deliberately and more effectively Manage knowledge more efficiently Pragmatic Thinking and Learning Refactor your Wetware Andy Hunt 288 pages ISBN 978 1 9343560 5 0 34 95 http pragprog com titles ahptl Ubuntu Kung Fu Award winning Linux author Keir Thomas gets down and dirty with Ubuntu to provide over 300 apne concise tips that enhance productivity avoid annoyances and simply get the most from Ubuntu You ll find many unique tips here that can t be found anywhere else Ubuntu Kung Fu Tips Tricks Hints and Hacks You ll also get a crash course in Ubuntu s flavor of system administration Whether you re new to Linux
18. Do This Christophe Porteneuve 330 pages ISBN 1 934356 01 8 34 95 i i Christophe Porteneuve http pragprog com titles cppsu pee The 2000 U S Census revealed that 12 of the population is severely disabled Sometime in the next two decades one in five Americans will be older than 65 Section 508 of the Americans with Design Accessible Disabilities Act requires your website to provide Web Sites equivalent access to all potential users But beyond care the law it is both good manners and good business EL Eu to make your site accessible to everyone This book shows you how to design sites that excel for all audiences Design Accessible Web Sites 36 Keys to Creating Content for All Audiences and 1 a Platforms Mere J Sudik Jeremy Sydik 304 pages ISBN 978 1 9343560 2 9 34 95 http pragprog com titles jsaccess ing t Don Start with the habits of an agile developer and use the team practices of successful agile teams and your project will fly over the finish line Practices of an Agile Developer Agility is all about using feedback to respond to change Learn how to apply the principles of agility throughout the software development s process establish and maintain an agile working Practices Es f an environment deliver what users really want eveloper use personal agile techniques for better coding and debugging use effective collaborative techniques for better teamwork move to a
19. Files Now your repository is starting to come together With one file it s pretty simple right now but as it grows some cleanup is necessary Report erratum Prepared exclusively for Frode Nilsen MANAGING FILES 4 62 Files need moving code needs to be copied around and some of the everyday cruft from working with your project needs to be ignored Renaming and Moving Files We all write flawless bug free code on our first pass Right Even though we would like to think that we do we sometimes get things wrong Naming a file incorrectly or putting it in the wrong directory is no exception You can move a file in Git by typing git mv original file lt new file gt The command tells Git to create new file with the existing file s content and it keeps the history and removes original filename Your Hello World page is not an index so let s move it prompt git mv index html hello html prompt git status On branch master Your branch is ahead of origin master by 1 commit L Changes to be committed use git reset HEAD lt file gt to unstage renamed index html gt hello html git mv is a convenience Git can detect the movement of a file but more steps are involved You have to move the file and then call git add on the new file and git rm the command to remove a file from the repository on the old file Go ahead and commit the new hello html move prompt g
20. Git and some of which you have to install yourself and links to online resources Finally in Appendix C on page 174 you ll find information on other books that are referenced throughout this one Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 TYPOGRAPHIC CONVENTIONS lt 13 Typographic Conventions A few typographical conventions are used throughout this book They are as follows Git Refers to the program as a whole when capitalized git Refers to the command you run on the command line italic Signifies new concepts files and directories Are displayed in this font prompt gt Comes before something you should type Longer commands may be broken up into several lines with a at the end of each line They can be typed as one line They re broken up in the book only so they fit on the page Online Resources Each chapter in Part II starts with a repository that looks like your repository does if you follow along with each of the examples throughout the book If you skip ahead you can get a copy of the repository by cloning it from GitHub You can find the repositories on GitHub from my profile http github com tswicegood The command you need to get the current repository is listed at the start of each chapter The book s web page on pragprog com is a great jumping off point for what s going on with the book From there you can drop me a note on the forums or make sugg
21. REMOTE 11486 html work boc lt meta name description meta name description content Information about Travis Swicg content Information about Travis lt head gt lt head gt lt body gt lt body gt lt hisTravis Swicegood lt hi gt lt hisTravis Swicegood lt hi gt lt p gt lt p gt Travis Swicegood is the author of Pragmat Travis Swicegood is the author of Py Version Control using Git Version Control using Git lt p gt lt p gt lt h2 Favorite Programming Languages lt h2 gt lt h2 gt Favorite Programming Languages lt h2 gt lt ul gt lt ul gt lt lisEr langs li gt lLisErlangz liz xl isPythonz li xl izPythonz li lt lisObjective C lt li gt lt lisObjective C lt li gt xlizJavascriptz li slisEMCAScriptz li lt ul gt lt body gt lt html gt a a p gt gt Y status 1 difference 1left 1 right 1 conflict Actions 1 Figure 5 1 OS X s FileMerge Utility That covers the creating and merging branches and shows how to han dle the conflicts that inevitably arise These are three of the areas where most of your time gets spent when working with branches Up next we move on to some housecleaning deleting branches 5 5 Deleting Branches Branches can outlive their usefulness The release was tagged the experiment was proven successful or failed When this happens you should delete the branch to keep your repository s branches from grow
22. United States of America ISBN 10 1 934356 15 8 ISBN 13 978 1 934356 15 9 Printed on acid free paper P2 0 printing March 2009 Version 2009 4 20 Contents Acknowledgments 9 Preface 10 Who s This Book For 2 22216 m Rm RR ES 11 Whats in This BOOK 2223 sioe mmm bee ee Rn 11 Typographic Conventions ossoa lees 13 Online ReSpuTCES soe 9 sone e e ee VR a aa aa we Re aras 13 I Welcome to the Distributed World 14 1 Version Control the Git Way 15 LI The Repository o saos e949 96m RR ome 16 L2 What Should You Store on a ek we dg 17 1 9 Working Trees 2 2 eom ee ee a 18 1 4 Manipulating Files and Staying in Sync 18 1 5 Tracking Projects Directories and Files 19 1 6 Tracking Milestones with Tags 20 1 7 Creating Alternate Histories with Branches 21 1 8 M ergig 26m ck Ro se ESA 9 aa a eG 22 L8 Locking ODUORS uses domm desk rex 24 LIO JNextO5teps 6 5 6 6466 oe be RR es OLS E ee es 25 2 Setting Up Git 26 2 1 Installing Git sok oe ee ee ea m ee es 26 2 2 Confid CUL uad eue hides Qwex uude oe 31 29 Usg Gits GUI 26 999 om emm m m Rm m RR 33 2 4 Accessing Gits Built in Help s 34 CONTENTS 4 6 3 Creating Your First Project 36 l GCreatinga Repository o e so n n 37 32 Making Changes 2 6 6 jb oe oem o 37 3 3 Starting to Work with a Project 40 3 4 Using and Understanding Branches 43 3 9 Handling Releases o aise eae e ew e 44 3
23. Versions In Section 4 3 Seeing What Has Changed on page 58 you learned how to use git diff to look at the differences between your working copy and the repository You can also use it to view the history within the repository prompt git diff 18f822e diff git a contact html b contact html index 64135cb 63617c2 100644 a contact html b contact html 13 6 13 10 p a href mailto tswicegoodGgmail com Gmail a p p a href http twitter com tswicegood gt Twitter lt a gt lt p gt lt body gt lt html gt Report erratum FINDING OUT WHO S TO BLAME 4 86 All the revision ranges and modifiers are the same as git log The only difference is that Git shows you all the changes mashed together in stead of incrementally Using git diff with tags is a great way to get statistics between releases With it you can figure out how many lines of code were changed and how many were removed There s another cool option for git diff that prints some statistics about the changes that have been made Just add the stat option prompt git diff stat 1 0 about htm 15 44 4 4 4 4 44 4 4 4 444 contact htm 23 E PH E PPP E RAT HT FORE BRK hello htm 13 rH EREeRR index html gne 4 files changed 51 insertions 9 deletions This is a great way to see the amount of code that has been touched in the last week or since the last tag Notice that I gave it a tag Gi
24. a bio link Now your repository looks like Figure 3 2 on the next page The add in a bio link is now placed after the final commit in the RB 1 0 branch Now for the final piece of cleanup deleting the release branch This might seem drastic but don t worry The tag you just created points Report erratum Prepared exclusively for Frode Nilsen HANDLING RELEASES 4 46 Add in a description element to the metadata add in hello world HTML V add lt head gt and lt title gt to index add in a bio link Figure 3 2 mysite repository after rebase to the same commit that the RB_1 0 branch does so everything is still intact You use git branch to delete the branch by adding the d parameter before the branch name prompt gt git branch d RB_1 0 Deleted branch RB_1 0 So how do you handle creating patches to the 1 0 x branch if you don t keep the release branch around That s easy create a branch off the tag you created Remember when you created the branch earlier You gave it the name of the branch you wanted to create the branch from Just change that to the tag and you re set prompt gt git branch RB_1 0 1 1 0 prompt gt git checkout RB_1 0 1 Switched to branch RB_1 0 1 A quick check of git log shows that you have only the three commits that were in your RB_1 0 branch prompt gt git log pretty onel ine 4b53779 Add in a description element to the metadata a5dacab add lt head gt and
25. again except add amend to the commit command prompt git commit C HEAD a amend Created commit 45eaf98 add link to blog 1 files changed 4 insertions 0 deletions That command introduces a new option to git commit C This option tells Git to use the log message from the commit specified in this case HEAD but it could have been any valid commit name as well instead of explicitly providing a new message You use the parameter in its lowercase form c to tell Git to launch the editor with the message already filled in so you tweak it before finalizing the commit Amending a commit should be done only when you are working with the last commit If you made a mistake and need to correct it after other commits have been made you want to use git revert which is up next 3 Ironically I had to use amend when writing this section of the book because I had a typo in one of the tags and didn t catch it until after I had committed Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 UNDOING CHANGES 4 93 Reverting Commits Sometimes code doesn t work out It requires a certain architecture or introduces a new third party software dependency that the rest of the team isn t on board with If you ve committed your changes already you need to undo the commits with the new change or revert them The simplest way to revert an existing commit is the git revert command It
26. and talked about git branch git tag and git rebase as well as got a quick glimpse of git clone Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 CLONING A REMOTE REPOSITORY lt 49 Part I has been a lightning fast tour of the concepts of VCS DVCS and Git This chapter particularly has been heavy on commands but thin on the why of the various commands Working through the exercise in this chapter you ve used Git to manage a simple repository for your HTML page project Now it s time to step back start with the basics and build up your knowledge of what Git is doing In the coming chapters we ll continue to build on the mysite repository as we explore even more of Git Report erratum Prepared exclusively for Frode Nilsen Part II Everyday Git 50 Chapter 4 Adding and Committing Cit Bas Now it s time to dig into Git Part I introduced you to Git Part II is about specifics We ll dig into Git and go through the basic commands you need in your day to day use of Git This chapter focuses on a few areas that we touched on in Chapter 3 Creating Your First Project on page 36 You ll now get a much deeper understanding of the following Adding files Creating commits Checking on what has changed Managing files We ll be building on the repository we started in Chapter 3 Creating Your First Project on page 36 If you skipped ahead to this p
27. and colleagues at SugarCRM and Ning who supported me while I wrote this book Finally I would like to thank my friends and family for their support and understanding while I wrote this book My wonderful wife Meg put up with the late nights and work weekends with very little com plaining Without her support and that from the rest of my friends and family this book wouldn t be here today Preface Development teams around the globe are changing They are dropping their clunky old centralized version control systems VCSs in favor of Git which is a lightweight distributed version control system DVCS and relative newcomer to the version control world First here s a quick overview a version control system is like a bank vault You take your valuables in our case as developers these valu ables are the source code we write and deposit them in the bank for safekeeping Each change you mark or commit is recorded and you can go back over the history just like you can review your bank statement In the Git world its like you walk around with your own vault that has an automated teller attached right to it You can fully disconnect from everyone else share what you want and of course keep track of your project s history The brainchild of Linus Torvalds Git was orig inally developed to track changes made to the Linux kernel Git has matured from the original rough collection of scripts Linus created in a few week
28. and the point you want to tag 1 0 and the branch RB 1 0 respectively You can view a list of tags in your repository by running git tag without any parameters Right now it shows only the 1 0 tag you just created prompt git tag 1 0 Report erratum Prepared exclusively for Frode Nilsen HANDLING RELEASES lt 45 Add in a description element to the metadata y add in hello world HTML add lt head gt and lt title gt to index add in a bio link Figure 3 1 mysite repository before rebase Now that your code is tagged you need to perform some cleanup You have two branches and each contains commits that the other does not know about The master branch the branch you started working on 2 0 features in needs to know about the new lt meta gt code you added in RB 1 0 To do this use the git rebase command Rebasing takes the changes from a branch and replays them on top of another branch Right now your repository looks like Figure 3 1 After rebasing it looks like Fig ure 3 2 on the following page First you need to switch back to the master branch That s the git check out command from earlier prompt git checkout master Switched to branch master Next you can run the git rebase command For our purposes right now it takes one parameter the name of the branch you want to rebase against prompt git rebase RB 1 0 First rewinding head to replay your work on top of it Applying add in
29. avoid First you can use a forward slash in a tag or branch name but it can t end with the slash This allows you to organize tags and branches into directory like structures You can also use periods in the name but Git will not allow the first portion of a path element in the name to begin with a period This means that releases 1 0 is a valid tag name but neither releases 1 0 nor eleases 1 0 is If you re familiar with the file system on Linux or BSD Mac OS X you probably recognize the issue with the second name Those operating systems treat a file or directory that begins with a period as something that should be hidden You can t use some special characters in a tag or branch name These include spaces tildes carets colons question marks aster isks and opening brackets None of the ASCII control characters anything lower than 040 or the Delete key ASCII 177 is allowed Don t worry if you don t know what those are or how to create them because it means you ll probably never create them by accident The only other rule in naming is that you can t use a double period any where in the name Remember the syntax for ranges we talked about in Section 6 2 Specifying Revision Ranges on page 82 Ranges use the lt first commit gt lt second commit gt syntax These aren t allowed in tag and branch names to keep from having any ambiguity Report erratum Prepared exclusively for Frod
30. blame to see the copy between files prompt git blame C b87524b7 original txt 1 This is the first line b87524b7 original txt 2 This happens to be the second line C copy txt C Cus b87524b7 original txt C 3 And this it is the third and final line C ja C b87524b7 original txt 4 This is the first line b87524b7 original txt 5 This happens to be the second line b87524b7 original txt 6 And this it is the third and final line Git displays not only the original commit name b87524b7 but also the original filename original txt git log can also show us when whole files have been copied when we pass it the same C C parameter When detecting for copies within the git log command we also have to pass the p parameter It tells Git to display the changes from each commit in addition to the normal log information prompt git log C C 1 p commit 540ecb73f652a882ad235c85b61ffb657d3d4969 Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 17 08 16 2008 0500 copy original to show cross file blame diff git a original txt b copy txt similarity index 10096 copy from original txt copy to copy txt Report erratum Prepared exclusively for Frode Nilser UNDOING CHANGES We can see that Git tells us that the copy ixt file is a 100 percent match for original txt Now that we ve covered the basics of change history it s time to bring out the inner revisionist histor
31. branch and merges it into another branch You can use this when you want to pull the entire history of one branch into another Lets demonstrate this by adding some new changes to the alternate branch you just created Add a new file called about html and add some information about yourself Once you ve created the new file add and commit it to your repository prompt git add about html prompt git commit m add the skeleton of an about page Created commit 217a88e add the skeleton of an about page 1 files changed 15 insertions 0 deletions create mode 100644 about html Now you have a commit on the alternate branch that doesn t exist on the master branch You can now use the git merge command to merge the two First you have to start by switching to the branch you want to use as your target for the merge In this case that s the master branch prompt git checkout master Switched to branch master Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 MERGING CHANGES BETWEEN BRANCHES lt 70 Next you can use git merge In its simplest form git merge takes the name of the branch you want to merge into your current branch prompt git merge alternate Updating 9a23464 217a88e Fast forward about html 15 t ttt 4 1 files changed 15 insertions 0 deletions create mode 100644 about htm l Now the changes from the alternate branch are merged into your
32. date Git can understand since 24 hours since 1 minute and beforez 2008 10 01 yes it is smart enough to parse that date even with the mixed hyphen and period You can also pass ranges of commits in by separating two revisions with oldest revision newest revision You should always specify the oldest revision first so Git can understand what you want prompt git log 18f822e 0bb3dfb commit Obb3dfb752fa3c890ffc781fd6bd5dc5d34cd3be Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 11 06 47 2008 0500 add link to twitter At first glance that output looks wrong We told it to show us the log from revision 18f822e to revision Obb3dfb The first time I used a com mand similar to this I thought it would include 18f822e but Git doesn t Instead Git interprets that range to mean every commit after 18f822e to 5ef8 HEAD is synonymous with the latest revision of the current branch in your repository In our earlier command we could swap out Obb3dfb with HEAD and get the same result Report erratum SPECIFYING REVISION RANGES lt 84 prompt gt git log 18f822e HEAD commit Obb3dfb752fa3c890ffc781fd6bd5dc5d34cd3be Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 11 06 47 2008 0500 add link to twitter You can drop the final HEAD from that range because Git assumes HEAD is what you mean if you leave the last value blank prompt git log 18f822e commit
33. entire history of your repository 9 3 Rebasing a Branch Branches are a great way to organize your work but keeping every thing in sync between branches has been branching s Achilles heel With merge tracking such as Git provides the effort required to keep everything in sync is greatly reduced but there is another way For example in Section 8 2 Handling Release Branches on page 112 you added code to the RB 1 0 1 branch There s a new paragraph that exists in the 1 0 1 tag that master doesn t know about yet You can rebase master against that tag so that the change is incorpo rated into the history of the master branch as if the master had always had that change We talked about git rebase earlier in Section 6 7 Rewriting History on page 94 where you used git rebase i to interactively rewrite the history You can use it without the i parameter to tell Git to rebase or rewrite the history in your current branch against an updated point on another Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 REBASING A BRANCH lt 126 branch Think of it as a way to replay the history of your branch as if it were created at the new updated point in your repository s history Let s start the rebase Run git rebase and provide it with the tag you re going to rebase against prompt git rebase 1 0 1 First rewinding head to replay your work on top of it Applying add in a bio link
34. file but not the entire Ant program Its not a hard exception though Sometimes storing a copy of Ant or JUnit or some other program in your repository can make sure the entire team is using the same version of the tools you use These should be stored separately from your project however Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 WORKING TREES 1 3 Working Trees So far we ve discussed the repository and talked about all the files yourre storing in it but we haven t talked about where you make all of your changes This happens in your working tree The working tree is your current view into the repository It has all the files from your project the source code build files unit tests and so on Some VCSs refer to this as your working copy People coming to Git for the first time from another VCS often have trouble separating the working tree from the repository In a VCS such as Subversion your repository exists over there on another server In Git over there means in the git directory inside your project s directory on your local computer This means you can look at the his tory of the repository and see what has changed without having to com municate with a repository on another server So how do you get this working tree in the first place Well you can start your own project and then tell Git to initialize a repository for it or you can clone an existing reposit
35. four pieces of information about each commit the commit name the author the date and the log message The first three are on the first three lines The rest of the entry until the next line beginning with commit is the log entry Sometimes our log messages aren t as descriptive as we thought they were when we view them six months later Often viewing the code that changed in conjunction with the log message can help jog our mem ories Adding the p option tells Git to display the diff that revision created Often you need to view only a set number of commits You can add 1 to the log command to limit the log to one commit 2 to limit it to two commits and so on For example git log 10 shows the last ten log entries You can view the log starting at a given revision by passing the revision as an option at the command line prompt gt git log 7b1558c commit 7b1558c92a7 755d8343352d5051384d98f104e4 Author Travis Swicegood lt development domain51 com gt Date Sun Sep 21 14 20 21 2008 0500 add in hello world HTML Note that I used a short commit name the first seven characters of the commit name Git tries to match any hash you provide it but it has to be unique Four or five characters normally matches but seven or eight is almost guaranteed to be unique Now that you have the basics down with git log it s time to dive into more complex ways of telling Git what commit or commits you re looking for 6 2 Spec
36. gc output on my book s repository looks like prompt gt git gc Counting objects 3918 done Compressing objects 100 2052 2052 done Writing objects 100 3918 3918 done Total 3918 delta 2103 reused 3440 delta 1852 Removing duplicate objects 100 256 256 done Your output will vary slightly of course based on the size of your repository s history The changes that git gc makes stick with your repository Once it has been run you don t need to run it again until there are more changes that need to be optimized So what does this optimization translate into Disk space Running the git gc command on my book s repository reduced the size of the repository by roughly 20 percent This isn t to say that Git normally isn t efficient The problem is that Git wants to be fast and efficient To achieve both it delegates some of the optimizations to later so you can run them when speed isn t an issue Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 EXPORTING YOUR REPOSITORY You can add the aggressive parameter to git gc to do even further opti mizations This comes at the expense of speed but can be worth it Git stores changes that were made in what it calls deltas git gc com presses those deltas when it runs by itself but it doesn t recalcu late them Adding aggressive tells Git to recalculate those deltas from scratch when it runs its optimization
37. have those you need to convert them to an SVN dump file using the cvs2svn tool prompt cd path to cvs rcs files prompt cvs2svn dumpfile svndump Creating the dump file allows you to filter out any unnecessary data by using tools such as svndumpfilter With your new svndump prepared now you need to create a Subversion repository to import it into You can do this by using the svnadmin create command prompt cd prompt svnadmin create tmpsvn prompt svnadmin load tmpsvn path to cvs rcs files svndump Assuming there were no problems loading the history into your tmpsvn repository now you re ready to import that into Git The process is the same as the one covered in Section 10 1 Communicating with SVN on page 136 prompt git svn clone file path to tmpsvn Now you know how to get your history out of Subversion and CVS and into Git You can even treat Subversion like a shared upstream reposi tory pushing changes back to it In the next chapter you ll learn how to manage upstream Git reposito ries through Gitosis 2 You can download this in source form directly from http cvs2svn tigris org or you can get it from your favorite package manager in Linux or MacPorts in OS X 3 http svnbook red bean com en 1 1 ch05s03 htmli svn ch 5 sect 3 1 3 Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 Chapter 11 Gitosis is a tool that shows off the br
38. hello html in 4333289e Oh that s right hello html didn t exist at commit 4333289e It was still index html at that point Run the command again with index html as the filename Notice that there s a between the end of the options and the actual filename That tells Git that you re specifying a file prompt git blame L lt body gt 2 4333289e index html 7b1558c Travis Swicegood 2008 09 21 14 20 21 0500 7 h1 Hello 7b1558c Travis Swicegood 2008 09 21 14 20 21 0500 8 lt body gt That covers the basics of git blame You ve seen it display when files have moved but it can also follow changes from copy and pasting You ll learn how to do that next 6 5 Following Content As we talked about in Section 4 4 Copying Files or Not on page 62 Git can track when the content moves within a file and even when it moves to another file This is useful when you re trying to track down the original commit and author of a few lines of code To keep from matching lines like a closing bracket in C or a simple constructor in Python Git tries to match at least three lines when it tries to detect a copy and paste Let s create a new file to demonstrate this functionality 2 Mastering Regular Expressions Fri97 is one such excellent book Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 FOLLOWING CONTENT 4 89 Call it original txt and put the following thr
39. ing out of control After you merge your changes back into your current branch such as the about2 branch you created you can use the d parameter on git branch to delete the old branch prompt git branch d about2 Deleted branch about2 Frode RENAMING BRANCHES lt 4 78 This works only when the branch you re trying to delete has been suc cessfully merged into the current branch you are on To demonstrate this lets switch back to the master branch Remember we haven t merged any of our changes from the about branch yet prompt git checkout master Switched to branch master prompt git branch d about error The branch about is not an ancestor of your current HEAD If you are sure you want to delete it run git branch D about Now if you are sure you want to remove the about branch without merging you can force it to be removed by swapping out the d for a D That tells Git not to check and to make sure that the branch you are trying to delete has been merged into the current branch Let s revisit renaming branches one last time before we wrap up this chapter on branches 5 6 Renaming Branches Branch names serve as a reminder as to what you re working with Sometimes those reminders need to change Sometimes you need to fix a typo Let s take our contact branch There was one method of contact when it started but now there s three Let s rename it to contacts prompt git branch m contact contac
40. li gt gt gt gt gt gt gt about2 about html ul You can see that there are two different names in the last li element The first is the commit you made to about earlier The second is the line you just added to about2 The conflict is prefixed by this HEAD about html The code that conflicted from the other branch is displayed after the separator and suffixed with the following line gt gt gt gt gt gt gt about2 about html The prefix and suffix lines tell you two things First any code that is preceded by lt lt lt lt lt lt lt is the code in your current branch and any code suffixed with gt gt gt gt gt gt gt is from the other branch Second the name of what you are trying to merge is included before the filename In this case it is the HEAD remember that s the name of the most current commit in your current branch that conflicts with the about2 branch Report erratum red exclusively for Frode Nilsen HANDLING CONFLICTS 4 76 For simple merges you can edit the file by hand to resolve the conflict Once you have saved your changes you need to stage and commit your changes like normal For more complex merges using a visual tool such as kdiff3 in Linux or opendiff on OS X is helpful Git can launch a merging tool by using the git mergetool command git mergetool attempts to locate a tool to handle the merge for you It will sometimes f
41. local branches it will show that you are not on a branch prompt git branch no branch about alternate contacts master new You can create a new branch and check it out with git checkout b like this prompt git checkout b from 1 0 Switched to a new branch from 1 0 Now you can start tracking changes directly again Like all good things in Git you can do this another way as well You can create a new branch using git branch or git checkout b and use a tag name as the second parameter prompt git checkout b another from 1 0 1 0 Switched to a new branch another from 1 0 Report erratum Prepared exclusively for Frode Nilsen 0 printing March 2 HANDLING RELEASE BRANCHES 4112 The git log output here shows that the only commits in the current branch are the original three commits that were there for the 1 0 tag Creating a branch from a tag can be useful for creating release branches to fix bugs or make small changes to previously released code Handling those release branches is the topic of the next section 8 2 Handling Release Branches Release branches are a place to prepare code for a release Teams nor mally use them to segregate code for a release What segregate means depends on the team The exact timing of a release branch depends on the team and your development style For simplicity s sake let s work with this definition a release branch is created when a project is feature complete
42. logged in It also doesn t run every time your server boots up Each operating system handles that a little differently I use nohup when I want to run git daemon even after I log out of my server but I don t need it to start up when I reboot my server The command I use looks something like this prompt nohup sudo u git git daemon base path srv example com repositories amp The final amp suffix detaches it from the current session and the nohup prefix detaches it from the current user A final note Gitosis is stable but still relatively new just like Git I have used it exclusively to manage my Git repositories for the better part of a year and never had any issues with its reliability It is tightly coupled with Git however so there may be incompatibility issues between different versions of Git I ran into one that was caused by a change in Git from version 1 5 x to 1 6 0 It has already been fixed but there s always the possibility that something like that will pop up If you run into any issues installing Gitosis you can try the book s forums or if IRC is more your thing the git channel on Freenode always has a few people with experience including usually Tv the devel oper of Gitosis 11 9 Closing Thoughts This brings us to the end of the book There s some additional infor mation in a few appendixes In Appendix A on page 158 you ll find recipes for the common tasks in Git Consider it your Git cook
43. now Depending on how fast your system is it may take a few seconds or a few minutes to finish installing Once it has finished you can verify that it installed correctly by running git version from the Windows command prompt Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 CONFIGURING GIT Git Setup Adjusting your PATH environment How would you like to use Git from the command line Use Git Bash only This is the most conservative choice if you are concemed about the stability of your system Your PATH will not be modified Run Git from the Windows Command Prompt This option is considered safe and no conflicts with other tools are known Only Git will be added to your PATH CO Run Git and included Unix tools from the Windows Command Prompt Both Git and the Unix tools will be added to your PATH Warning This will override Windows tools like find exe and sort exe Select this option only if you understand the implications gle com p msysait Figure 2 2 Git extras To start the command prompt click Start and then Run In the dialog box that pops up type cmd and click OK Once it is started type git version If everything is successful Git outputs its version number like it does in Figure 2 3 on the next page Regardless of which operating system you re running some basic con figuration is necessary before you can start using Git Let us cover that now
44. of Git over other popular DVCSs however is its ability to continue to not only pull but also push changes back to Sub version The command to push changes back to Subversion is git svn dcommit It takes each of the commits you ve made locally and commits them back to your Subversion repository one by one During this process it rebases your copy so each of your local commit reflects the information from the Subversion server Just like git svn rebase this is to make it easier for git svn to figure out what it has already synced You can use the n option to tell Git you want to do a dry run In this mode it looks through your history and lists all the commits it would send to the Subversion repository Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 IMPORTING FROM CVS 44 146 10 6 Importing from CVS If you re coming to Git from CVS there are some hurdles you must jump over compared to Subversion In fact the most reliable method for converting a CVS repository to Git is to convert it to a Subversion repository first using the cvs2svn command cvs2svn is a tool for con verting a CVS repository to a Subversion repository Git ships with a tool for importing CVS repositories called git cvsimport Since the cvs2svn command is much more stable to a Git repository we ll focus on it To start with you need to get revision control system RCS files from your CVS repository Once you
45. on many Linux and Mac computers The configuration needs a little tweaking to look decent on a Mac You can add configuration values to the gitk file in your home directory to customize the interface I like my development interfaces to all use the same font at the same size Panic Sans at 11 points 1 Panic Sans is part of the Coda package which is available online at http www panic com coda THIRD PARTY TOOLS lt 168 My gitk file looks like this set mainfont Panic Sans 11 set textfont Panic Sans 11 set uifont Panic Sans 11 bold git gui git gui provides an interface to the basic commands you need when working with a repository You can use it to view files that are not being tracked changed files and what is staged It also lets you stage changes and make commits It is platform independent so you can use it in any operating sys tem but the cross platform capabilities mean it doesn t integrate as smoothly with your operating system the way tools such as Tortoise SVN CVS do gitweb gitweb is a web front end to Git repositories You may have seen it in action at http git kernel org or http repo or cz gitweb incorporates every feature you need to view your repository in a web interface It is bundled with Git s source code in the gitweb directory Full infor mation on how to install it and how to configure it is available in the INSTALL and README files in that directory B 2 Third Par
46. parts in the book in case you can t wait to learn more about something we re talking about I encourage you to follow along with the examples in this chapter and the rest of the book executing all the commands yourself We learn via repetition whether it s our multiplication tables in grade school or typing a Git command into the command prompt l If you re interested in the processes of learning Andy Hunt s Pragmatic Thinking and Learning Hun08 is an excellent book on the topic CREATING A REPOSITORY 3 1 Creating a Repository Creating a repository in Git is simple but it seems peculiar if you re coming from Subversion or CVS Your repository is something that exists separate from your copy of it in most VCSs Your repository in Git is stored right alongside your working tree in a directory called git To create a repository in Git you first need to decide where you want to store your project s code In this example we re going to create a simple HTML page so let s call our project mysite You need to create a directory of the same name then change into it and type git init The whole process should look something like this prompt mkdir mysite prompt cd mysite prompt git init Initialized empty Git repository in work mysite git You re done You now have a Git repository that is ready to start track ing your project But there must be more you cry Actually no Setting up a Git reposi tory is an e
47. pass the aggressive option This may take a while Though l ve personally seen fourteen plus CPU hours spent compressing a newly cloned repository with more than 31 000 commits Subversion doesn t know how to respond to a request such as Give me your entire history so git svn queries it one revision at a time For a large repository with tens of thousands of commits this can take nearly a whole day Notice in the earlier git svn clone command that I included a prefix parameter That tells git svn to add a prefix such as the remote reposi tory names for remote branches to all the Subversion based branches Without adding a prefix you end up with remote and local branches of the same name You don t have to add this parameter but it does make the output of git branch a much easier to digest If old commits aren t important to you you can use the r option to specify what revision to start cloning at Specifying a revision clones the history of that one revision You have to run another command to pull the rest of the changes The command git svn rebase is the same com mand we ll use in the next section to pull changes from our upstream Subversion repository after our initial import 10 4 Keeping Up to Date with a Subversion Repository Whether you are communicating with an active Subversion repository or you used git svn clone r to make your initial clone you can pull changes from your Subversion repository in two w
48. s demonstrate this really quickly That last commit that reverted those two files isn t necessary So let s undo it prompt git reset hard HEAD HEAD is now at 45eaf98 add link to blog That resets your repository back to the commit before HEAD It s like that commit that reverted the two files never happened 6 7 Rewriting History Revisionist historians view history as a living thing something that needs to be reevaluated from time to time to make sure the assump tions that were made in the past still apply Looking over your code as part of a formal code review is a great way to make sure the assumptions you made last week or last month still apply Git lets you take this a step further though by allowing you to not only review the history of your code but to rewrite it Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 REWRITING HISTORY There are a few instances where this is useful Reorder the history so it makes more sense This is the hardest to quantify but you ll know it when you see it One commit or maybe more seems out of place and logically fits in a different order e Squash several commits into one commit You realize after the fact that multiple commits should actually be in one big commit because they all relate to the same issue Break one commit into multiple commits This is the reverse of squashing After looking through the changes you realize
49. separate from your local branches origin is the default remote repository name assigned to a repository that you create a clone from Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 PUSHING CHANGES lt 105 Now that you can fetch and pull changes from remote repositories let s talk about pushing changes to a remote repository 7 4 Pushing Changes Getting changes from upstream repositories is only half of keeping in sync with everyone else on your team You also need to be able to push changes back to an upstream repository to share the changes with everyone else As we talked about in Section 1 4 Manipulating Files and Staying in Sync on page 18 pushing changes is sending changes to another repository This is the step you go through to send your commits with another repository It s an extra step from the traditional VCS world where a commit is automatically sent to a centralized repository Git makes a few assumptions when you call git push without any param eters First it assumes you re pushing to your origin repository Second it assumes you re pushing the current branch on your repository to its counterpart on the remote repository if that branch exists remotely Git pushes only what has been checked in so any changes you have in your working tree or have staged are not pushed prompt git push Counting objects 11 done Compressing objects 100 7 7 done Writing
50. submodule commands this takes the name of the submodule you re working with as its parameter prompt git submodule update hocus Initialized empty Git repository in work new magic hocus git remote Counting objects 7 done remote Compressing objects 100 5 5 done remote Total 7 delta 0 reused 7 delta 0 Receiving objects 100 7 7 done Submodule path hocus checked out 20cc9ddc65b5f3ea3b871480c1e6d8085db48457 Now your hocus directory has all the files from the 20cc9dd commit that you tracked This brings you up to speed on how to set up a submodule but right now it always tracks this one commit What do you do when you want to change what you want to use That s up next Changing Which Commit Is Tracked by a Submodule Gits submodules don t track the latest commit in the repository they track an individual commit It always starts tracking whatever the HEAD the latest commit is when you add the submodule You have to tell Git when you want to change the commit it s tracking This might seem odd at first for those with a Subversion background Subversion tracks the repository and automatically pulls the latest commit whenever you run an update To track an individual revision you have to explicitly set that up That might seem more convenient at first glance but it can introduce problems What happens when a bug is introduced in the repository you were tracking or when you have one revision of a remo
51. that one commit has multiple changes in it that you want to have as indi vidual commits If you re coming from a traditional VCS such as Subversion or CVS that list might seem like voodoo The idea of changing a commit after the fact can take getting used to but actually reordering commits breaking one commit into multiple commits That s too much Thats the power of having a private repository that s not connected with other developers though If you share your changes instantly like all centralized VCS such as Subversion or CVS do you can t make any changes without risking unresolvable conflicts when someone tries to update with a repository that has changed The tool for this kind of voodoo is the interactive mode of Git s rebase command git rebase i Using it you can craft the history Here s the last three commits to the repository prompt git log pretty format h s HEAD 3 45eaf98 add link to blog 540ecb7 copy original to show cross file blame 222cb82 adding copied lines to showcase git blame In the next section you ll learn how to move the 45eaf98 commit to the beginning Reordering Commits git rebase in interactive mode is the tool to use to rewrite history Launching interactive mode starts your editor for you to make the changes you want You ll remember how Git looks for an editor from Section 4 2 Committing Changes on page 55 You have to provide the rebase command with the revision you want to work f
52. the keydir directory of the same name with a pub extension For example the key for my user is located in keydir travis pub To add a new user you need their public SSH key Each developer who wants access to your repository needs to generate their key on their computer It can be generated using the command you used earlier but it has to be done on their computer Each key is specific to a particular computer Once you have a copy of their public key add it to the keydir directory named with the name you want to use for them and then add that name to the repositories you want to give them access to Once you ve committed those changes to your local repository you need to push it to the Gitosis server with a quick git push command 11 7 Adding New Repositories The initial configuration that Gitosis creates has one configuration repository but you can manage as many repositories as you like If you want to you can add new writable lines to the gitosis admin group but that means everyone with access to your repositories has access to change Gitosis configuration A more secure solution is to create two groups one for administrators and another for normal developers Here s a sample configuration gitosis group gitosis admin writable gitosis admin members travis Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 ADDING NEW REPOSITORIES 4 153 group team wri
53. to commonly used commands You never have to type svn checkout or svn commit because a simple svn co or svn ci does the trick for you Reading through this book and trying the examples you might have tried those same aliases with Git and got an error that you weren t using a Git command Git doesn t ship with all those aliases like Subversion but it does give you a better option You can add your own aliases via git config You can add git ci as a shortcut to git commit with the following prompt git config global alias ci commit That works for any Git command so you can customize your environment just the way you want it Substitute the portion after alias for the alias you want to create and you re set There is an important difference to remember between the first method of committing staged commits and committing all changes or a partic ular file s changes The last two methods commit the file as it exists the moment you execute the commit The first method commits the change you staged This means you can stage a change make a change to the file and then commit the change you staged while still having a file that is changed in your working tree Think of a staged area as a buffer You add to the buffer with git add That buffer stays there until you save it by executing git commit Speaking of staged commits you still have that change staged from the previous section Let s leave it there for a little bit longer
54. to correct changes The other gotchas revolve around adding new content directly to a sub module s repository First before you make a change check out the branch you want to apply the changes to Remember that the sub module is detached from the normal branches A quick git checkout will fix that Then once your changes have been committed you have to make sure your changes are available from the remote repository before you share your changes to the submodule checkout Git will behave unexpectedly if the commit of your submodule references is not available from the remote repository when you try to run git submodule update That brings us to the end of this chapter on organization You learned how to use tags for the first time and how you can use them to orga nize the milestones of your repository You also learned about release branches and how they can help you organize your repository as you prepare for a release Now you know that there are two different ways to organize your repos itories and projects storing everything in one big repository and storing everything in individual repositories The chapter closed with a look at Git submodules and how you can use them to track remote repositories as independent parts of your repository With what you learned in this and the previous chapters you now know what you need to about Git to start being productive with it In the next chapter we ll cover a few of the lesser used part
55. your repository to try to figure out when the bug got introduced git bisect is a tool that helps with that process git bisect works by stepping through your repository s history based on a known bad commit and a known good commit It walks you through your repository letting you mark a commit as good or bad until you isolate the commit that created the bug Consider this example Your repository for your project has a 1 0 tag and your current code is working toward the 1 1 release of your project Your beta testers reported a bug in the new releases that they can t reproduce in version 1 0 of your software Now you have a good point and a bad point in your repository to check against so you can use git bisect to start walking through the history to isolate the bug You can see what this repository looks like in Figure 9 2 You can see that there are three possible commits that caused this break First things first create a test case that demonstrates the bug Test it against the bad commit to make sure it doesn t pass and then test it against the one you know is good to prove that it works there Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 BISECTING YOUR REPOSITORY lt 132 good commit bisect starts here bad commit Figure 9 3 git bisect starts in the middle Now move back to the bad commit and start the bisect process by calling git bisect start then git bisect bad an
56. 1 files changed 19 insertions 0 deletions create mode 100644 contact html Squashing and straight merges both have their uses Sometimes you need just one commit though Cherry picking is useful in these cases Cherry Picking Commits Sometimes you need to merge only one commit between branches and don t need to do a full merge The full merge might be a bad idea because the branch has features that you can t use yet or other changes that aren t ready for this branch yet Report erratum Prepared exclusively for Frode Nilsen MERGING CHANGES BETWEEN BRANCHES lt 72 So when do you need to pull just one commit Maybe it s a bug that has been fixed or there s a class that needs to be shared between branches You can pull those individual commits using git cherry pick Just like the name implies it cherry picks a commit and adds it to your current branch Let s run through a quick albeit contrived exam ple and create a third commit in your contact branch First you need to make sure you re on the contact branch prompt git checkout contact Switched to branch contact Next now that you ve switched add a new link to another way to con tact you such as your Twitter account and commit it prompt git commit m add link to twitter a Created commit 321d76f add link to twitter 1 files changed 4 insertions 0 deletions With the commit name 321d76f in hand you can cherry pick it any wh
57. 5de Ocb04ad HEAD 2 commit third commit 71bc515 HEAD 3 commit second commit 5e685de HEAD 4 checkout moving from master to reflog Report erratum red exclusively for Frode Nilsen USING THE REFLOG 44 130 I shortened the commit on the second line of the output so it would fit on the page This output reads in reverse chronological order like the regular git log Notice that there are two commits with the message third commit Commit Ocb04ad is the first commit while 1041334 is the second commit after git rebase removed 71bc515 So to restore to your first third commit all you have to do is check out that commit prompt git checkout Ocb04ad Note moving to Ocb04ad which isn t a local branch If you want to create a new branch from this checkout you may do so now or later by using b with the checkout command again Example git checkout b new branch name HEAD is now at Ocb04ad third commit As the message tells you you re not on a real branch but you can create one here with a simple git checkout b Not being on a branch doesn t stop you from viewing the history though Using git log you can now see your second commit has been restored prompt git log pretty format h s Ocb04ad third commit 71bc515 second commit 5e685de initial commit Of course you don t have to explicitly check out the branch to create it You can just as easily use git branch to create the branch im
58. 7 Working with Remote Repositories on page 100 Clone a Repository prompt gt git clone lt some repository gt Clone a Repository but Download Only the Last 200 Commits prompt gt git clone depth 200 lt some repository gt Add a New Named Remote Repository prompt gt git remote add lt remote repository gt lt repository url gt Show All Remote Branches prompt gt git branch r Create a Local Branch from a Remote Branch prompt gt git branch lt new branch gt lt remote branch gt Create a Local Branch from a Remote Tag prompt gt git branch lt new branch gt lt remote tag gt Fetch Changes from Origin Repository but Do Not Merge into Local Branch prompt gt git fetch Fetch Changes from a Remote Repository Other Than Origin but Do Not Merge prompt gt git fetch lt remote repository gt Fetch Changes from a Remote Repository and Merge into Current Branch prompt gt git pull lt remote repository gt Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 GIT TO SVN BRIDGE 44 165 Fetch Changes from Origin Repository and Merge into Current Branch prompt git pull Push Local Branch to Remote Branch prompt git push remote repository local branch remote branch Push Local Branch to Remote Branch of Same Name prompt git push remote repository local branch Push New Local Branch to Remote Repository prompt git push remote
59. 9 git fetch 104 git gc 123 124 143 git init 103 git IRC channel 173 git log 81 84 86 97 112 113 130 Git Mailing List 173 git merge 70 71 git mergetool 76 126 git mv 62 git pull 104 git push 105 152 git rebase 45 95 126 129 144 git remote add 107 git remote rm 108 git reset 73 94 98 git revert 93 git rm 62 git status 59 63 71 73 121 git submodule 117 119 120 git submodule add 117 git submodule init 119 git submodule update 119 121 git svn clone 141 143 git sun dcommit 145 git svn fetch 144 git svn rebase 143 145 git tag 110 111 git gui 168 GIT SH lt B REFLOG git sh 171 git svn 140 142 GitHub 13 102 109 171 gitk 33 167 GitNub 170 Gitorious 169 172 Gitosis 147 155 admin setup 149 150 configuration 151 152 dependencies 148 initialization 151 installation of 147 149 public repository 154 155 repositories for 152 154 server configuration 150 gitosis init 151 gitweb 168 GitX 168 Graphical user interface see GUI GUI 33 34f gzip 47 H Hashes options for 84 SHA 1 39 Help built in 34 35 History repository 80 99 blame 86 88 changes undoing 91 94 commands for 162 compacting 123 124 content tracking 88 91 log of 81 82 reviews of 94 99 revision ranges 82 85 version differences 85 86 Hook scripts 147 Hosting 171 172 HTTP 102 Hunk 54 I Ignoring files 63 64
60. Branches prompt git branch r Show All Local and Remote Branches prompt git branch a Create a New Branch from the Current Branch prompt git branch new branch Report erratum Prepared exclusively for Frode Nilsen Check Out Another Branch prompt git checkout some branch Create a New Branch from the Current Branch and Check It Out prompt git checkout b new branch Create a Branch from Another Starting Point You can create a branch from any start point within the history of the repository The start point can be another branch a commit name or a tag prompt git branch new branch start point Overwrite the Existing Branch with a New Branch prompt git branch f some existing branch lt start point gt Move or Rename a Branch only if new branch does not exist prompt git checkout m existing branch name new branch name gt Overwriting any existing branch prompt git checkout M existing branch name new branch name gt Merge Another Branch into the Current Branch prompt git merge some branch Merge but Don t Commit prompt git merge no commit some branch Cherry Pick Commit prompt git cherry pick commit name Cherry Pick but Don t Commit prompt git cherry pick n commit name Squash One Branch s History into Another prompt git merge squash some branch Delete a Branch only if branch has
61. CONTENTS lt 8 IV Appendixes 157 A Git Command Quick Reference 158 Al Setup and Initialization es 158 A2 Normal Usage 24 he Gl 6 abe po M X ey a 159 Ad DBrIABnOhB6sS 224 GG Rx a EUR a rede 160 JL History sa cee Hee eRe e 9o kc XR eom Roe cm e eo 162 AS Remote Repositories lt s cesse coe Rr es 164 AO Gitto SVN Bridge 22235 eom yo wg 165 B Other Resources and Tools 167 B 1 Extras Bundled with Git 167 B 2 Third Party Tools l l 168 B 3 Git Repository Hosting 171 B 4 Online Resources 2 6 6 4 6 9 moo eS 172 C Bibliography 174 Index 175 Report erratum Prepared exclusively for Frode Nilsen Acknowledemen Although my name is on this book as the author it is only here because of a long list of people Please indulge me while I take a moment to thank them Thanks to Dave Thomas and Andy Hunt for taking the chance on a new author The entire team they ve put together at Pragmatic Bookshelf is amazing I owe a special thanks to my editor the ever helpful Susannah Davidson Pfalzer I would also like to thank all of those who offered me feedback on the book as it progressed through beta form Especially helpful was the great team of technical reviewers Chuck Burgess Pieter de Bie Stu art Halloway Junio Hamano Chris Hartjes Mike Mason John Mertic Gary Sherman Jacob Taylor and Tommi Tv Virtanen Thanks also to the wonderful teams of developers
62. Chapter 7 Working with Remote Repositories on page 100 introdu ces you to the concepts around sharing your work with others through remote repositories The social aspect of any version control system is its killer feature and Git is no different Once you know how to use Git and interact with other developers repositories you ll learn about some organizational techniques in Chapter 8 Organizing Your Repository on page 109 to keep your repository sane Finally we round out Part II with Chapter 9 Beyond the Basics on page 122 which introduces you to some commands you ll find useful for specialized situations These chapters all have lots of examples to follow along with but keep in mind they are jumping off points for how to use Git to work with your code s history Once you get more comfortable feel free to experiment Part III is all about administration and is not required reading if someone else on your team or in your company handles that for you Chapter 10 Migrating to Git on page 136 shows you how to handle migration to Git from other popular VCSs and Chapter 11 Running a Git Server with Gitosis on page 147 teaches you how to administer your public repositories with Gitosis We close out with a few appendixes In Appendix A on page 158 you ll find a command reference so you can quickly find out how to do common commands In Appendix B on page 167 you ll find coverage of some extra tools some that ship with
63. Commands s 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 quit 8 help If you want to stage files that are not being tracked yet you can use the fourth option It works like the others so I won t show it again Patch mode is the most useful feature of interactive mode It starts out like the other modes You can choose which file or files you want to add via patch mode Once you make your choice you are presented with a diff of the changed files and given the option to add the changes or not It looks something like this What now 5 staged unstaged path 1 unchanged 1 1 index html Patch update gt gt 1 staged unstaged path sls unchanged 1 1 index html Patch update gt gt diff git a index html b index html index e812d0a ca86894 100644 a index html b index html 6 7 6 7 body lt h1 gt Hello World h1 ul lt li gt lt a hrefz bio html Biography a li 4 lt li gt lt a href about htm1 gt About lt a gt lt 1i gt lt ul gt lt body gt lt html gt Stage this hunk y n a d e Now you have the option of adding this hunk or denying it A hunk is a change within the file Consecutive changes are treated as one hunk Each different area in a file is treated as its own hunk Report erratum Prepared exclusively COMMITTING CHANGES 4 55 From the prompt typing y accepts the change n skips it and a and d add or deny all the rest of
64. EBASING A BRANCH lt 127 prompt gt git rebase continue Applying add in a bio link a bunch of additional lines saying Applying Applying copy original to show cross file blame Remember how you renamed index html to hello html using git mv in Sec tion 4 4 Managing Files on page 61 Check your hello html file now It now contains the new paragraph that was added in 1 0 1 This is a pretty simple case There was only the initial conflict and then the changes were pretty straightforward Let s look at a few of the more complex cases Say that you re following the Git repository of your favorite language or framework You might be maintaining a branch with some custom changes on top of the normal code There s a couple of things that might happen First if you submitted one of your changes and it was accepted Git is smart enough to realize that the change has been applied It won t try to apply your change again if it s already been made Another possibility is a conflict You dealt with a simple conflict the process is always the same Fix the conflict and then call the git add and git rebase continue like you did Of course you can also call git rebase with skip or abort to either skip that particular commit or completely abandon the rebase process respectively The onto parameter provides another interesting way to rewrite your history For example you have three branches master the contacts branch t
65. HTML 10 http www kernel org pub software scm git docs 11 http www methods co nz asciidoc this c ACCESSING GIT S BUILT IN HELP version to your local computer Look for the latest version of the git htmidocs file Now you ve gone through the Git installation and done the basic con figuration You have Git running so now it s time to start using it In the next chapter we ll walk through a basic project so you can start to get familiar with Git 12 http kernel org pub software scm git Prepared exc Chapter 3 reating Your First Proj Now it s time to dig into Git Up to this point we have talked about abstract ideas and getting set up That changes in this chapter We re going to work on a small HTML project and use Git to track it Don t worry if you don t know HTML The markup we re using here is simple and easy to follow even if you aren t familiar with HTML In this chapter we ll do the following Create a repository Add some files and make some changes Create a new branch Tag a release and clean up our repository release Clone a repository Once we re finished youll know the basics you need to get started with Git This chapter is a high level overview There are a lot of new concepts and commands introduced to get you started We ll be covering the commands and concepts introduced here pretty quickly but each section has references to later
66. NAL REPOSITORIES Adding a New Submodule Let s demonstrate this behavior First we need to create a new reposi tory that will house our submodule repository Let s create a repository called magic prompt gt mkdir work magic prompt gt cd work magic prompt gt git init Initialized empty Git repository in work magic git With this empty repository initialized you can use git submodule to view the submodules associated with this repository prompt gt git submodule prompt gt Since there are no submodules defined yet it doesn t return anything Adding a new submodule is straightforward You use the git submodule add command It has two required parameters The first is the reposi tory the second is the path where you want to store the repository For example let s add the hocus repository a small repository hosted on GitHub that I created to use for the book And to keep things clear let s put it in the hocus directory You can use the command on one line without the those are here to make the command fit on the page prompt gt git submodule add git github com tswicegood hocus git hocus Initialized empty Git repository in work magic hocus git remote Counting objects 7 done remote Compressing objects 100 5 5 done remote Total 7 delta 0 reused 7 delta 0 Receiving objects 100 7 7 done Now when you rerun git submodule hocus is displayed prompt gt git submodule 20
67. Obb3dfb752fa3c890ffc781fd6bd5dc5d34cd3be Author Travis Swicegood developmentQdomain51 com Date Sat Oct 4 11 06 47 2008 0500 add link to twitter With ranges you can swap out the commit name for a tag name too This is useful for seeing what has changed since a particular tag and for looking at the revision history between two tags prompt git log pretty format h s 1 0 HEAD Obb3dfb add link to twitter 18f822e add contact page 217a88e add the skeleton of an about page 9a23464 rename to more appropriate name 6flbf6f Change biography link and add contact link 4333289 add in a bio link Notice that this time I added the pretty parameter to git log The for mat h 96s option tells Git to display short hashes and the first line of the commit log which is the subject A more common usage is pretty oneline but the output from it is too wide to fit on this page There s a bunch of different formats you can use The git log manual page lists them all If your git log command with ranges doesn t generate anything make sure it s a range that can actually work Remember the oldest revision has to be specified first If you don t do that Git won t complain it just won t show you anything Another common way to specify a revision is by its relationship to another revision There are two operators you can use e A caret acts like a minus one 181822e translates into the revi sion that comes before the revision tha
68. S 2008 09 22 07 54 28 0500 11 ul 7b1558c index html Travis S 2008 09 21 14 20 21 0500 12 lt body gt Using numbers is often convenient A lot of the time you have an edi tor open with the line numbers displayed when you need to figure out what s going on in a file but Git provides another way to specify the start and end regular expressions 1 Git uses POSIX regular expressions if you re curious about what type of regular expression you can use Report erratum Prepared exclusively for Frode Nilsen FOLLOWING CONTENT 4 88 Many books have been written on regular expressions so I won t cover them here other than to show you an example You can write the blame command we ve used previously using a regular expression like this prompt git blame L lt body gt 2 hello html 7b1558c index html Travis S 2008 09 21 14 20 21 0500 12 lt body gt 7b1558c index html Travis S 2008 09 21 14 20 21 0500 13 lt html gt Of course a lot of times the output from blame isn t going to be helpful Perhaps the coding standard changed and someone was performing some cleanup You can use any of the methods we talked about in Section 6 2 Specifying Revision Ranges on page 82 to specify where you want to look For example if you want to look at the hello html file before the 4333289e commit you can use this command prompt git blame L lt body gt 2 4333289e hello html fatal no such path
69. UILT IN HELP 4 0 Git Gui mysite work book mysite Current Branch master Unstaged Changes Modified not staged File index html ee 3 7 3 10 Re index html lt title gt Hello World in Git lt title gt lt meta name description content hello world in Git gt lt head gt lt body gt lt hi gt Hello World lt hi gt lt ul gt gt lt li gt lt a href bio html gt Biography lt a gt lt 1i gt lt ul gt lt body gt lt html gt Commit Message 9 New Commit Amend Last Commit Rescan il Stage Changed Commit C Push Ready Figure 2 4 git gui running 2 4 Accessing Git s Built in Help Git has an extensive user manual that is available from the command line and online From the command line you can type this prompt git help command Just replace command with the command you want help on and Git displays the user manual entry for that command The documentation is not installed by default if you build from source Some package managers distribute it as a separate git doc package If you re building from source you need to call the doc and install doc targets when running make Git requires AsciiDoc in order to convert the documentation from plain text into the manual form Don t worry if you have trouble installing the documentation you can always access it online at kernel org or you can download the
70. a It gives you the ability to craft exactly the commit you want to make prior to making it To be able to craft the changes though you have to add them first git add is the command for that Like all good Git commands there s more to adding files than just call ing git add You can specify several different options to change how git add behaves and a couple of the options are even useful You can use Git s interactive add mode to select which files or parts of files to stage for a commit You start it by adding the i option This starts up the interactive shell for staging changes adding new files and even staging part of a file Let s change the index html file so we have something to stage Change the Biography link to About It now looks like this lt li gt lt a hrefz about html About a li Now run git add i Git displays a prompt like the following one when you start up interactive mode prompt git add i staged unstaged path T unchanged 1 1 index html Commands sx 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 quit 8 help What now Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 ADDING FILES lt 53 You have several options now Typing 1 generates this same status that is shown when you start up To add a file you can type 2 to stage the file What now 2 staged unstaged path Js unchanged 1 1 index html Update Th
71. age When Git tries to launch an editor it looks through the following values in this order 1 GIT EDITOR environment variable core editor Git configuration value VISUAL environment variable EDITOR environment variable a B WwW N Git tries vi if nothing else is set When you use the editor to create your commit message by adding the v option you can tell Git to add a diff in the editor showing the changes Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 COMMITTING CHANGES you are about to commit There will be a lot of lines that begin with All of those are ignored when Git reads the commit message Like nearly every command in Git there are a few different ways to handle a commit Before we create a new commit let s look at the three ways to generate a commit First you can call git add in some form for the files or changes if you re using git add o that you want to commit This stages those changes for commit and calling git commit closes the loop The process looks like this prompt gt git add some file prompt git commit m changes to some file That s an example of a bad commit log message but it does fit nicely on a printed page so I ll use it here as an example In a real commit message don t just state the obvious make sure to explain why you made the changes too Remember from the Joe Asks on page 42 that your commit message should
72. ags act like bookmarks in your repository You can use them to jump back to the point in the repository that you tagged You can tag any commit in Git for any purpose you can think of The most common use of tags is to mark when the code in your project is released That allows you to go back to the code you released if you need to fix or change something later Tags in Git are read only unlike the tags you might be familiar with if you re coming from Subversion This means you can t make a change to the contents of a tag as if it were a normal branch This is a much better way to handle tags You can be sure that the tag is exactly what was tagged and hasn t changed since it was created The command to work with tags in Git is git tag Just like git branch you can call it without any parameters to see what tags you currently have prompt git tag 1 0 That s the tag we created in Chapter 3 Creating Your First Project on page 36 Let s create a tag called 1 1 To do that call git tag again but this time provide it with the tag name 1 1 prompt git tag 1 1 Git does not provide any visible feedback that the tag was successfully created You can call git tag without any parameters though to see your newly created tag prompt git tag 140 1 1 Git s tag command may be quiet if it succeeds but if there is a problem it lets you know For example if you try to create a tag using a name that is not valid a tag name with spac
73. ail The normal practice is to exit with a 1 You can t exit with the exit code 125 unless you want to skip a commit and have git bisect move to the next commit Generally you do not want to skip a commit unless you just can t test whether a commit is good or bad git bisect run is the command you use to automatically run this script For example if you create a script called run tests you can invoke it like this prompt git bisect start HEAD 1 0 Bisecting 1 revisions left to test after this d3289f8ab4916f58134a7e5c813ca91c13dd6a70 commit message prompt git bisect run work run tests running work run tests git bisect continues running just like you were doing it manually except it uses the exit value from the script called work run tests Every time the script returns an integer other than O it is treated as a bad commit Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 BISECTING YOUR REPOSITORY lt 134 Notice that this command references a file in another directory This is to make sure Git doesn t change the file that git bisect run is trying to execute Using a file outside the repository to drive your tests isn t a necessity but can help avoid any problems git bisect is one of those commands that you may never have to use but if you do it can be a lifesaver Coupled with an automated test suite that can be run from the command line you can use it to t
74. an create a branch called new like this prompt git branch new Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 CREATING A NEW BRANCH 4 4 68 Git doesn t give us any visible feedback that it created a new branch but we can check by running git branch again without any parameters prompt git branch master new There s our new branch called new Notice that the master branch has an asterisk by its name That s to signify which branch is currently checked out The checked out branch is the branch that your current working tree reflects Of course you want to be able to make changes to the files in your newly created branch To do that you have to check out the branch You do that with the git checkout command like this prompt git checkout new Switched to branch new That s all it takes to switch Run git branch again without any parame ters to see that the current branch has changed prompt git branch master new Most of the time when you create a branch you want to immediately check it out so you can start working with it Git provides a quick shortcut to do that You can create a branch and check it out in one step by adding the b parameter to git checkout Lets create another branch using git checkout b Each branch has to have a unique name so you have to choose something besides master or new Let s go with alternate to keep it simple prompt git checko
75. andling Conflicts What happens when you edit the same file in different ways in two different branches and then try to merge them Git tries to merge them together but sometimes it can t It is called a conflict when Git can t automatically merge the commits together Conflicts occur most commonly when the same area in a file is changed in different ways in each branch For example you might use a different variable name in each branch Git can t tell which one you want to use so it stops with a conflict and lets you fix it Let s demonstrate how a conflict works First let s create a new branch called about to add our work in prompt git checkout b about master Switched to branch about Next add a list of a few of your favorite programming languages Save the file and then add and commit it to the repository prompt git add about html prompt git commit m a list of my favorite programming languages Created commit Olfe684 a list of my favorite programming languages 1 files changed 7 insertions 0 deletions Now create a second branch called about2 but don t switch to it just yet prompt git branch about2 about Before you switch branches add another language to your about html file and commit your change prompt git commit m add Javascript to list a Created commit 9e114ac add Javascript to list 1 files changed 1 insertions 0 deletions Now you have a change that exists in the about bra
76. ar formats The value you pass to format changes and instead of piping the output through gzip with zips you send it directly to the file where you want to save it Of course there s often more to handling a release you might have wiki pages to update acceptance tests to run against the code and so on but every one of those tasks is dependent on the tools and methods you use By using tags you can manage how Git interacts with those processes you have and Git s archive command can help you create the releases of your project s source code That wraps up the basic commands but so far we ve covered only the commands that you use locally Next we ll cover cloning which is what you need to get a project from someone remotely Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 CLONING A REMOTE REPOSITORY 3 6 Cloning a Remote Repository One thing we haven t touched on yet is remote repositories You ve built up the mysite repository using commands that interact locally Git can also deal with remote repositories however so you can share your work and get copies of others repositories To get started with a remote repository you need to clone it using the git clone command Cloning a remote repository does what it sounds like It creates a complete copy of the remote repository that you can start working with I already have my copy of mysite shared on GitHub a Git re
77. ark milestones with tags How to track an alternate history with a branch What merging is How Git handles locking All of these ideas revolve around the repository so let s start there THE REPOSITORY 1 1 The Repository The repository is the place where the version control system keeps track of all the changes you make Most VCSs store the current state of the code along with when each change was made who made it and a text log message that explains why they made the change You can think of a repository like a bank vault and its history like the ledger Each time a deposit what is called a commit in VCS lingo is made your VCS tool adds an entry to the ledger and stores the changes for safekeeping Originally these repositories were accessible only if you were logged directly into the machines they were stored on That doesn t scale so tools such as CVS and later Subversion were created They allowed developers to work remotely from the repository and send their changes back using a network connection These systems follow a centralized repository model That means there is one central repository that everyone sends their changes to Each developer keeps a copy of the latest version of the repository and when ever they make a change to it they send that change back to the main repository The centralized repository is an improvement over having to directly access the machine where the repository lives but i
78. at diff doesn t show the changes that aren t staged yet though You can compare everything thats in your working tree including your staged changes against whats in your repository To do that execute git diff and add HEAD to the end prompt git diff HEAD diff git a index html b index html index e812d0a 5fdc539 100644 a index html b index html 6 7 6 8 body lt h1 gt Hello World hi ul lt li gt lt a hrefz bio html Biography a li lt li gt lt a hrefz about html About a li lt li gt lt a href contact htm1l gt Contact lt a gt lt li gt lt ul gt lt body gt lt html gt HEAD is a keyword that refers to the most recent commit to the branch you re in You don t need to worry about that branch part just yet but it does come back up Let s create a commit so our changes are tracked prompt gt git commit a m Change biography link and add contact link m About is shorter so easier to process m We need to provide contact info Created commit 6flbf6f Change biography link and add contact link 1 files changed 2 insertions 1 deletions Now you know all the normal commands to get you going You can add files commit changes to the files you re tracking and even compare the changes you ve made against what s in your repository Let s get into some housecleaning commands now such as moving copying and even ignoring some files Managing
79. at the filename index html is listed Remember when you created this file It was originally named index html That second col umn if it s present is Git s way of telling that this change was origi nally in another file After that it displays the committer s name and the time the commit was created It s followed with the line number and then the line of code Of course you rarely need to see the entire file annotated Git makes it easy to annotate a portion of a file with its L option This tells Git to display only a certain set of line ranges It takes single parameter a start end The start and end can be numbers For example the following loads the blame for lines 12 and 13 of the hello html file prompt git blame L 12 13 hello html 7b1558c index html Travis S 2008 09 21 14 20 21 0500 12 lt body gt 7b1558c index html Travis S 2008 09 21 14 20 21 0500 13 lt html gt The ending number doesn t have to be a specific number You can spec ify it as N or N to specify a range This generates the same output as the previous command prompt git blame L 12 42 hello html 7b1558c index html Travis S 2008 09 21 14 20 21 0500 12 lt body gt 7b1558c index html Travis S 2008 09 21 14 20 21 0500 13 lt html gt Using the N notation allows you to subtract that many lines You can use L 12 2 to show lines 12 and 11 of your file prompt git blame L 12 2 hello html 4333289e index html Travis
80. ault transfer protocol when it talks to remote repositories Next up if you plan on using Git to talk to a Subversion repository like we ll discuss in Chapter 10 Migrating to Git on page 136 you need to install the subversion perl package from the Libs category Also in that category you should grab tcltk so you can take advantage of the inte grated graphical interfaces for Git that we ll talk about in Section 2 3 Using Git s GUI on page 33 Finally make sure to install your favorite text editor from the Editors category Vim emacs or even Pico is fine but you need to have an editor installed to take advantage of some of Git s commit log features If you don t know what a commit log is don t worry you will once yourre finished with the next chapter Git on MSys There is a fork of Git that aims to bring Git to Windows using the under lying Windows architecture It is not officially supported yet but is in the process of being merged back into the official Git repository A project has been started on Google Code called Git on MSys whose goal is to take that forked code and create an easy to install Git pack age for Windows The installer can be downloaded from the project s website 9 After you download the installer double click it to start the installation process The first screen displays information about the software you re about to install You can see the screen in Figure 2 1 on the next page Click Next to continue
81. ays Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 KEEPING UP TO DATE WITH A SUBVERSION REPOSITORY M4 Joe Asks Whats with That Error If you cloned a project within a repository that isn t present in the oldest commit you might see errors similar to these W Ignoring error from SVN path probably does not exist 175002 RA layer request failed REPORT request failed on test svn bc 100 REPORT of test svn bc 100 Could not read chunk size Secure connection truncated svn svnrepo W Do not be alarmed at the above message git svn is just searching aggressively for old history As the second warning the lines that start with W says don t worry When git svn tries to clone your Subversion repository it starts at the oldest revision it can access and keeps moving for ward until it can find a revision that contains the code you ve referenced The warning is telling you is that it couldn t find the code at the oldest revision it requested It continues through the history until it finds the revision where the project you re trying to clone first exists The first is git svn fetch It pulls all the remote changes into their remote branch but doesn t try to merge them into your local branch This is also the command you use to grab new branches from Subversion The second and the one that gets more use is git svn rebase It works like git svn fetch followed by git re
82. base It pulls all the commits from your upstream Subversion repository and then rebases your current branch against the remote branch Just like with git rebase if you have a local commit that has been applied on Subversion it will not apply that patch again when rebas ing Also like its regular Git counterpart git svn rebase can t run when there are uncommitted changes in your working tree Report erratum Prepared exclusively for Frode Nilsen A 144 PUSHING CHANGES TO SVN lt 145 Alternative t lonin version R itor Cloning a Subversion repository can be a time consuming pro cess l ve cloned large repositories that have taken more than twenty CPU hours If you re trying to clone a large existing repository ask around for a bootstrap repository before you start cloning yourself A bootstrap repository is a tarball of a Git repository that has been cloned from the Subversion repository you want to track In the open source community bootstrap repositories are nor mally updated every week or so Using a bootstrap repository all you have to do is type git svn rebase to grab all the changes since the last time the bootstrap was updated That s a lot faster than cloning an entire history 10 5 Pushing Changes to SVN We ve covered everything you need to know if you re migrating to Git and leaving your Subversion repository behind Share your newly created repository and skip this section One of the benefits
83. been merged into current branch prompt git branch d branch to delete Report erratum Prepared exclusively for Frode Nilsen A 4 even if branch has not been merged into current branch prompt gt git branch D lt branch to delete gt History These commands show you your history including where your code has been who did what and when changes and statistics Many of these commands are covered in more detail in Chapter 6 Working with Git s History on page 80 Show All History prompt gt git log Display Log with Patch Showing Change prompt gt git log p Limit Log to Show One Entry prompt git log 1 Limit Log to Show Twenty Entries and Patches prompt git log 20 p Show Commits from Past Six Hours prompt git log since 6 hours Show Commits Older Than Two Days prompt git log before 2 days Show Log for Single Commit Three Commits Prior to HEAD prompt git log 1 HEAD 3 Or prompt git log 1 HEADAAA Or prompt git log 1 HEAD 1 Show Commits Between Two Points lt start point gt and lt end point gt in the following example can be a commit branch or tag name You can also mix different names prompt gt git log lt start point gt lt end point gt Prepared exclusively for Frode Nilsen HISTORY 44 162 Report erratum HISTORY Show Log History as One Liners prompt git log pretty oneline Show Stats of Affected Lines for Each Line Ent
84. book In Appendix B on page 167 you ll find information on a few of the extra tools and resources available to you as a Git user The book finishes up with Appendix C on page 174 It lists all the other books referenced throughout this book 2 http forums pragprog com forums 64 Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 CLOSING THOUGHTS lt 156 I hope you ve enjoyed reading this book as much as I have enjoyed writing it It has been a great learning experience and a lot of fun and I hope that has come through in the book If you have any questions feel free to stop by the book s forum and drop me a line 3 http forums pragprog com forums 64 Part IV Appendixes 157 A 1 Appendix A This appendix is your quick reference for how to perform common Git tasks Each section focuses on one type of task This appendix is light on content and heavy on commands If you re skipping ahead and aren t familiar with the concepts of Git now would be a good time to flip through Chapter 1 Version Control the Git Way on page 15 Setup and Initialization Before you start working with Git you have to configure it Before you can start working on a new project you have to initialize it This section covers commands related to the initial configuration and setup of Git Configure Global Username Email prompt gt git config global user name Your Name prompt g
85. cc9ddc65b5f3ea3b871480c1e6d8085db48457 hocus Git submodules track a particular revision within the remote reposi tory That revision is noted here by the hash and then the name you gave it hocus is displayed You probably noticed the minus sign before the hash This is telling you that the hocus submodule has not been initialized That s simple enough to fix prompt gt git submodule init hocus Submodule hocus git github com tswicegood hocus git registered for path hocus Report erratum Prepared exclusively for Frode Nilsen USING GIT SUBMODULES TO TRACK EXTERNAL REPOSITORIES lt 118 This adds an entry to git config so Git understands that the hocus direc tory contains a submodule Now with everything added and initialized you can see that you have some changes in your repository prompt gt git status On branch master 3 Initial commit Changes to be committed use git rm cached file to unstage new file gitmodules new file hocus The gitmodules is a plain text file that stores all the information about your submodule Git tracks this file inside the repository That way when you share your repository with someone else Git has the infor mation it needs to get their submodule set up too Now it s time to commit these changes Any simple log message will do prompt gt git commit m initial commit with submodule Created initial commit f24a0d9 initia
86. cd add secondary email 1 files changed 4 insertions 0 deletions Report erratum Prepared exclusively for Frode Nilsen this copy MERGING CHANGES BETWEEN BRANCHES lt lt 71 Now you have two commits in your contact branch You can squash these two commits back into the master branch as one commit First you need to switch back to the master branch prompt git checkout master Switched to branch master Now call git merge and pass it the squash parameter Adding the squash option tells git merge to take all the commits from the other branch and squash them into one commit prompt git merge squash contact Updating 217a88e 2f30ccd Fast forward Squash commit not updating HEAD contact htm 19 4 4 4 4 4 4 4 4 4 4 4 4 44 1 files changed 19 insertions 0 deletions create mode 100644 contact html Now both of your commits from contact have been applied to your work ing tree and are staged for a commit but they have not been committed You can run git status to see the changes prompt git status On branch master Your branch is ahead of origin master by 1 commit L Changes to be committed use git reset HEAD file to unstage new file contact html 3 All that s left now is for you to commit the change like any other commit prompt git commit m add contact page m has primary and secondary email Created commit 18f822e add contact page
87. d finally git bisect good some commit or tag The session looks something like this prompt git bisect start prompt git bisect bad prompt git bisect good 1 0 Bisecting 1 revisions left to test after this d3289f8ab4916f58134a7e5c813ca91c13dd6a70 commit message Once you mark the second commit git bisect moves you to another place in the repository It takes the commits between the two known points splits them in half and checks out that point This makes your reposi tory look like Figure 9 3 Now rerun your tests to prove this commit good or bad In this case the commit is bad so mark it as such with git bisect bad prompt git bisect bad Bisecting 0 revisions left to test after this 1318f2a48089ea36c082d7e69cbd7c04b489821ec commit message Now there is just one commit left to try with no more commits left between this and the good commit Logically you can determine at this point that if the previous commit was good and all the commits after this point are bad this one must be the cause A quick run of the unit tests proves that it is Marking it as bad causes Git to realize it has hit the last possible bad commit and shows the log entry for it Now you ve narrowed the history down to the commit that was bad All that s left to do is figure out exactly which change in the commit caused the problem and fix it git bisect moves you off your branch as it steps through each commit You need to move back on
88. dentials already created now you need to initialize Gitosis Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 INITIALIZING GITOSIS 44 151 11 5 Initializing Gitosis Gitosis comes with a program gitosis init to handle initialization gitosis init doesn t require any options but it must be run as the user you created in the previous section If you used the recommended git user your init command looks like this prompt sudo H u git gitosis init path to id rsa pub Initialized empty Git repository in srv example com repositories gitosis admin git Reinitialized existing Git repository in srv example com repositories gitosis admin git This initializes Gitosis and its repository All that s left now is the con figuration If you got an OSError exception continue reading this section Otherwise you can skip ahead If you ve installed Git in a location that s not in your normal PATH you ll get this error instead of the successful output shown previously This is because the gitosis init command can t find Git To fix this you need to make sure the Git commands are available to the git user You can do this by modifying SPATH variable for the user Gitosis is running as or you can make sure that the Git commands are available to the user by adding a symbolic link to the git binary in one of the directories in the Gitosis user s PATH 11 6 Configuring Gitosis N
89. domain51 com Those are the only two required configuration values but Git allows you to configure more than 130 different settings Most of these you ll never need to tweak but there is one extra change that is useful if you like color coded output The setting color ui is used to control colors in the user interface of Git Setting it to auto adds color codes around the various output of Git whenever you re viewing the output in the terminal 7 You can view a list of all the configuration settings by using the git helo config command if you installed the documentation or by visiting http www kernel org pub software scm git docs git config html _variables Report erratum Prepared exclusively for Frode Nilsen this copy is P2 0 printing March 2009 USING GIT s GUI You can turn this setting on with the following command prompt gt git config global color ui auto To me the color coded output is much easier to scan especially the diffs the differences between commits but some people do prefer straight up text so color coding isn t turned on by default Thats all there is to configuring Git you re ready to start using it Before we jump into our project in Chapter 3 Creating Your First Project on page 36 lets cover some of Git s graphical user interface GUI options 2 3 Using Git s GUI Git comes with a Tcl Tk GUI interface You can run it from within your project s directory by typing g
90. e Since I didn t want to add an extra file and commit to the repository I had the swp line added to my git info exclude file We ve covered the basics now in this chapter Everything else builds on these basics Start adding things to your repository and then commit your changes Now you have the basics down Now it s time to start learning about branches Other VCSs treat them as an afterthought but in Git they re so important to use that we need to cover them up front Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 Chapter 5 Understanding and You can use Git with a single branch the default master and get all the benefits of a VCS Git will track the history let you collaborate with other developers and make sure you don t accidentally delete some thing important But using Git this way is like buying a racing car and using it for your commute It will get you there but you never get to use the car to its potential in the 8 a m rush hour traffic Branches are a fundamental part of Git In this chapter you ll learn what branches are and how to do the following Create new branches Merge changes between branches Handle conflicts Delete branches Rename branches Handle release branches We re going to be working with the repository that you ve created up to this point If you ve skipped ahead you can clone the repository from its GitHub repository pr
91. e Nilsen 2 0 printing March 2009 TRACKING MULTIPLE PROJECTS 34115 That s it Branches and tags can be named about anything that is a valid file or directory name just like your normal file system and you can organize them into directory like structures to help sort them Of course we haven t gotten into the specifics of tags yet so let s cover them 8 4 Tracking Multiple Projects Most organizations have multiple projects Even if they are different parts of one product they all need to be segregated so everyone on the team can find the code they need without having to sift through all the code You can handle multiple projects with Git in a couple of ways You can store all your projects in one repository or you can have individual repositories for each project There are pros and cons to each and we ll cover them in the following sections Multiple Projects One Repository The first and most straightforward method is creating one repository and storing multiple projects within it You can do this by creating a different top level directory for each project within your repository This will be familiar to those with a Subversion background because this is how Subversion handles multiple projects within a repository This is a convenient way to store all the projects together so you have to clone only one repository to get access to everything This works well for projects that need to have a common history such as a p
92. e Subversion and CVS commands you re familiar with to their Git counterparts the Subversion mapping is shown in Figure 10 1 on the next page and the CVS mapping is shown in Fig ure 10 2 on page 138 Communicating with SVN Many companies today use Subversion to manage their version control repositories It was designed to be a compelling replacement to CVS and has succeeded in many areas It is much easier to understand with its clear understandable command structure and its atomic commits are much easier to track Git didn t set out to become a replacement to Subversion or any other version control system for that matter but its features make it a com pelling replacement to Subversion COMMUNICATING WITH SVN 4 137 Common Subversion Commands in Git svnadmin create git init git clone svn update git pull git add git commit git status git checkout branch svn merge branch git merge branch svn revert lt file gt git checkout lt file gt Figure 10 1 Common Subversion commands in Git Report erratum Prepared exclusively for Frode Nilsen COMMUNICATING WITH SVN 138 Common CVS Commands in Git cvs d repo init git init cvs d lt repo gt checkout lt module gt git clone cvs update dP git pull git add git commit git status cvs co r branch git checkout branch cvs update j git merge cvs update C git checkout lt fi
93. e have the basics adding new files modifying existing ones and looking at the repository s history out of the way now let s get into something meatier and turn our attention to branches Report erratum Prepared exclusively for Frode Nilsen STARTING TO WORK WITH A PROJECT S id Joe Asks What Should My Commit Log Message Contain Determining what to put in your commit log message can be tricky when you first start out At its barest the message should contain all the metadata explaining the why of the commit Here s a few good commit messages e Changed from nested if elseif statements to switch for readability e Removes experimental code after proven not useful Crafting the perfect log message is something of an art It s something that you can learn by looking at the logs of other successful projects Git s own log is a treasure trove of excellent commit messages Spend a minute or two with each commit you make and sum marize the changes the same way you would as if you were explaining them to another developer sitting next to you A great rule of thumb is to write a simple one line sentence that tersely explains the commit and then spend another few sen tences fully explaining your commit Another thing to keep in mind when writing your commit mes sage is who is going to read it If humans are the only ones ever reading your commit messages then straight English is fine If a program is going t
94. e project already has a history but how do you push your changes to a remote repository if you created it with git init Just add the repository you want to push to by using the git remote add command we covered in Section 7 5 Adding New Remote Repositories on the preceding page Call the remote repository origin if it is going to be the repository you want to push changes to by default For example your session should look something like the following if you want to add a remote repository at git example com repos pocus git prompt git remote add origin git example com repos pocus git prompt gt git push origin master SOU pute sols GIC E To do a one off pull from her repository you use git pull and her reposi tory It might look something like this prompt gt git pull git ourcompany com dev erin git That s OK for a one time pull but if you re going to be doing it more than once adding an alias can save some keystrokes To add a new named remote repository use git remote add name repo url This command adds Erin s repository prompt git remote add erin git ourcompany com dev erin git Now you can use erin instead of the full repository any time you need to push or pull some changes So the pull we just executed now looks like prompt git pull erin HEAD warning no common commits remote Counting objects 6318 done remote Compressing objects 100 2114 2114 done remote Total 6318 delta
95. e repositories 106 107 adduser 150 Aliases 58 apt get 167 Archive 46 AsciiDoc 34 Authentication 103 D Bisecting repository 131f 132f 131 134 Branches 22f 21 22 43 45 65 79 changes in reflog 129 checking out 68 commands for 160 conflict handling 74 77 creating 67 68 defined 66 67 deleting 77 78 merging 69 73 names for valid 114 115 rebasing 125 128 release 112 114 renaming 78 79 see also Merging Branching and merging 10 Buffer 58 Bugs 113 119 131 CMS Centralized repository model 16 Changes undoing 91 94 Checked out branch 68 cherry pick 73 Cloning remote repositories 103 104 Index repositories 48 118 Color control 32 42 61 Commit messages 42 83 Commits breaking down 98 cherry picking 71 orphaned 129f reordering 96 squashing 70 96 submodules and 119 see also Changes undoing Committing files 55 58 Configuration 31 33 Configuration management CM 25 Conflict resolution 23 74 77 Conflicts 74 Content tracking 88 91 Conventions 13 110 Copying files 62 CPAN 142 Creating branches 67 68 CVS 138f importing from 146 cvs2svn 146 D de Bie Pieter 33 Deleting branches 77 78 Directed acyclic graph DAG 66 Directories tracking 56 Distributed architecture 10 Distributed version control systems DVCSs 10 15 16 see also Git Documentation 35 see History repository DVCSs see Distributed version control system
96. e sure changes are ready before you push them By keeping all your changes local until they are ready you leave yourself the option of rewriting your repository s history without worry ing how it affects others Once you push your changes you lose some of that flexibility well only if you want to keep everyone else on your team talking to you Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 UNDOING CHANGES 4 92 When you push changes then change your history and push those changes that are different you can cause problems for people who already have the first set of changes you published For more infor mation on pushing changes see Section 7 4 Pushing Changes on page 105 Now that we ve covered the dangers in what we re about do to let s get to the good stuff Up first amending commits Amending Commits We ve all been there You re writing code in a new still sort of unfamil iar language and forget a full stop at the end of a line or leave off a semicolon Correcting these small problems with Git is simple Make the correc tion stage the change and add amend when you commit To demonstrate add a link to your blog or a website you frequent in your contact html file except put a typo in it prompt git commit m add link to blog a Created commit c3531c4 add link to blog 1 files changed 4 insertions 0 deletions Now fix the URL and commit the changes
97. e the b and t options if your branches and tags directories are in different locations Likewise if your trunk isn t named trunk you can use the T option prompt git svn clone prefix svn s svn svnrepo sunshine Initialized empty Git repository in work sunshine git Using higher level of URL svn svnrepo sunshine gt svn svnrepo sunshine This may take a while on large repositories branch from tags tags prototype Found possible branch point svn svnrepo sunshine branch tswi cegood speed r1 305a06a00d6048fe36ee01bb96b7c770cc30317e trunk A tests basic use cases py r2 a7f1299c2821f788d64218cc4e366ebe13202105 A src sunshine init py A src sunshine framework py etc etc r50 c534dfb90a8365842af86fde85065d76baca260a trunk Checked out HEAD svn svnrepo sunshine r50 l http svnbook red bean com en 1 1 ch04s07 html Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 KEEPING UP TO DATE WITH A SUBVERSION REPOSITORY lt 143 hrinking the Size of Your R itor If you clone a Subversion repository of more than 100 or so com mits you might notice that a lot of disk space has disappeared after the clone is finished Just like you would after a few hundred commits remember To run git gc on a fresh Subversion clone as soon as possible to reduce the amount of disk space taken up If it s the first thing you do after you clone the repository you can safely
98. eable How you structure these modules within repositories is up to you Git allows you to structure your repositories however you like You can create a new directory in the repository for each project so the projects share a common history or you can create a new repository for each project Coming up with the perfect balance is challenging for someone new to the VCS world In Chapter 8 Organizing Your Repository on page 109 we ll cover some of the ways you can structure your repository We ve covered the basics now You know what a repository and your working tree are You know that your project is just how you lay out the contents of your repository Now let s explore tags 1 6 Tracking Milestones with Tags As projects progress they hit milestones Maybe you follow an agile methodology and have weekly development cycles where some new fea ture is added every week or maybe you re on a traditional cycle where updates are released every few months Either way you need to keep track of what state your repository was in when you passed that milestone Tags give us the tool to do that They mark a certain point in the history of the repository so you can easily reference them later Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 CREATING ALTERNATE HISTORIES WITH BRANCHES A tag is simply a name that you can use to mark some specific point in the repository s history It can be a major m
99. ects 3 done Writing objects 100 3 3 214 bytes done Total 3 delta 0 reused O delta 0 To git example com test git new branch master gt master Now you re set Other users who have access can clone your repository and push changes to it too if you gave them permission to write to the repository On an open source project your repository needs to be accessible by the public at large You might even need to expose your repository on your local VPN to everyone in the company but you don t need to keep track of who is logging in to read its contents Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 SETTING UP A PUBLIC REPOSITORY lt 154 You can set up your repository to allow anonymous read only access using git daemon which we ll cover next 11 8 Setting Up a Public Repository The one last thing you might need to do is set up the read only portion of your repository You have to do this only if you want to share your work with other developers without having to set up a user for them This is most common in open source development where anyone can read from the repository Setting this up requires two steps First you have to configure your repository for sharing with Gitosis Second you have to run git daemon to respond to the requests To configure Gitosis you need to edit the gitosis conf name from earlier This time add a new section called repo with the na
100. ee lines in it This is the first line This happens to be the second line And this it is the third and final line Once you ve saved your new file add it to the repository and commit prompt git add original txt prompt git commit m commit of original text file Created commit b87524b commit of original text file 1 files changed 3 insertions 0 deletions create mode 100644 original txt Now let s edit that file and duplicate the entire file Just copy and paste the first three lines onto the next three lines and save it Running git diff from the command line shows output similar to this prompt git diff diff git a original txt b original txt index 4d9f742 350f1bb 100644 a original txt b original txt 1 3 1 6 This is the first line This happens to be the second line And this it is the third and final line This is the first line This happens to be the second line And this it is the third and final line Commit this change so Git knows about it Now we can utilize the git blame command to view the history of each line of the file line prompt git blame original txt b87524b7 1 This is the first line b87524b7 C 2 This happens to be the second line b87524b7 C 3 And this it is the third and final line 5 222cb821 C 4 This is the first line 222cb821 5 This happens to be the second line 222cb821 6 And this it is the third and fi
101. eed to work on your own However the distributed in distributed version control means you ll normally be working with other people on your projects This chapter is about how to interact with projects on remote reposito ries You ll learn the following What the different types of remote repositories are How to create a copy of a remote repository How to stay up to date with remote changes How to share your changes by pushing to a remote repository How to work with remote branches How to add new remote repositories I m going to deviate for a minute Instead of having cloning instructions up front I ve added the instructions in Section 7 2 Cloning a Remote Repository on page 103 Before we dive into working with remote Git repositories let s talk a little bit about the different networking options you have to connect to different repositories Network Protocols Git communicates with remote repositories over a network That net work can be your internal LAN a VPN or the Internet Git provides three protocols for communicating with remote repositories SSH git HTTP HTTPS NETWORK PROTOCOLS d 101 git github com tswicegood mysite chp6 git Username Server Path to Repository Figure 7 1 Components of an SSH URL SSH Accessing a repository over Secure Shell SSH is similar to accessing a repository directly from the file system with one exception Before the path to the repository you add
102. eference to this highly regarded language Programming uby The Pragmatic i Up to date and expanded for Ruby version 1 9 Complete documentation of all the built in classes modules and methods Complete descriptions of all standard libraries Learn more about Ruby s web tools unit testing and programming philosophy Programmers Guide Programming Ruby 1 9 The Pragmatic Programmers Guide Dave Thomas Dave Thomas with Chad Fowler and Andy Hunt 992 pages ISBN 978 1 9343560 8 1 49 95 eS SEG of Ruby Series http pragprog com titles ruby3 Agile Web Development with Rail Rails is a full stack open source web framework with integrated support for unit functional and integration testing It enforces good design R l ile Web principles consistency of code across your team J ie evelopment and across your organization and proper release with ils management This is the newly updated Second Edition which goes beyond the Jolt award winning first edition with new material on Socoee Battion e Migrations RJS templates Respond to L NX e Integration Tests Additional ActiveRecord ey features Another year s worth of Rails best Dave Thomas practices David Hetnemeier Hansson Agile Web Development with Rails Second Edition Dave Thomas and David Heinemeier Hansson with Leon Breedt Mike Clark James Duncan Davidson Justin Gehtland and Andreas Schwarz 750 pages ISBN 0
103. en t retrieved until he got familiar with git reflog Report erratum Prepared exclusively for Frode Nilsen USING THE REFLOG E 129 This commit used to be part of the branch but now is orphaned Q Figure 9 1 A commit that was orphaned by git rebase The reflog keeps track of when a branch changes Remember in Chap ter 5 Understanding and Using Branches on page 65 that we talked about how branches are only a pointer to the latest commit in that line The reflog tracks all those changes Viewing it you can find the commit you need to check out to restore a branch For example lets create a simple repository and mess it up Create a new repository with a single commit and then create a branch and add two more commits The contents can be whatever you want you just need the commits in place Now using git rebase or git rebase i which you read about in Section 9 3 Rebasing a Branch on page 125 and Section 6 7 Rewriting History on page 94 delete the first of your commits on the second branch Now your branch should look like Figure 9 1 You can verify what your repository s history looks like by using git log That history is what you expect After git rebase i deleted the one com mit there are two commits in the history Now check the reflog you ll see it knows about a lot more commits prompt git reflog 1b41334 HEAD 0 commit third commit 5e685de HEAD 1 checkout moving from reflog to 5e68
104. en t seen yet but don t worry well cover how to use it in Sec tion 6 6 Resetting Changes on page 94 prompt git reset hard HEAD HEAD is now at 18f822e add contact page Now that the last commit is removed you can run git cherry pick again with the n parameter prompt git cherry pick n 321d76f Finished one cherry pick Notice that Git stopped at Finished one cherry pick this time You can run git status and see that the new file has been added and is staged and ready for commit prompt git status On branch master Your branch is ahead of origin master by 2 commits Changes to be committed use git reset HEAD lt file gt to unstage modified contact html Now you can proceed to cherry pick another change You can commit the changes with whatever message you would like once all the commits have been cherry picked Go ahead and commit the change But don t add a message with m The editor will come up with the commit message of the commit you just cherry picked prompt gt git commit Created commit Obb3dfb add link to twitter 1 files changed 4 insertions 0 deletions That covers the basics of merging So far our merges have been pretty straightforward and easy but what happens if there is a problem merging Handling those conflicts is the subject of the next section Report erratum Prepared exclusively for Frode Nilsen HANDLING CONFLICTS 74 5 4 H
105. ere Remember the commit names are universally unique so your commit name will be different from the one I created Let s bring it over to the master branch prompt gt git checkout master Switched to branch master prompt gt git cherry pick 321d76f Finished one cherry pick Created commit 294655e add link to twitter 1 files changed 4 insertions 0 deletions Of course this example isn t too impressive since your contact branch has only that one change but it does demonstrate the raw steps you need to take to perform a cherry pick Imagine you created a new class in one branch while you re refactoring some existing code maybe a class that implements a generic pattern such as a registry It s generic enough that you want to reuse it but it s stuck in another branch that you can t merge completely because you don t want or need all the functionality in that branch You can use git cherry pick to pick that change out By default a new commit is created with the changes from that cherry picked commit This is OK in most cases but what if the code you need is in several commits Report erratum Prepared exclusively for Frode Nilsen MERGING CHANGES BETWEEN BRANCHES lt 73 To cherry pick multiple commits give git cherry pick the n parameter That tells Git to do the merge but stop before creating a commit Let s demonstrate First lets remove it with git reset This command is something you hav
106. ere The blog and Twitter com mits can be squashed together So let s start another rebase this time against the commit before the Twitter link commit Obb3dfb prompt git rebase i Obb3dfb launched configured editor pick Obb3dfb add link to twitter pick b87524b commit of original text file pick 4f7621d add link to blog pick be53bab adding copied lines to showcase git blame pick 8c764d3 copy original to show cross file blame Report erratum Prepared exclusively for Frode Nilser REWRITING HISTORY 4 97 Rebase 18f822e 8c764d3 onto 18f822e Commands p pick use commit e edit use commit but stop for amending S squash use commit but meld into previous commit If you remove a line here THAT COMMIT WILL BE LOST However if you remove everything the rebase will be aborted dk Xk dk dk Gk Gk Gk Gk Gk Gk i This time move pick 4f7621d to come after pick Obb3dfb and change pick in the moved line to squash After you re done the first five lines should look like this pick Obb3dfb add link to twitter squash 4f7621d add link to blog pick b87524b commit of original text file pick be53bab adding copied lines to showcase git blame pick 8c764d3 copy original to show cross file blame Save and exit again After the rebase starts the editor will come back up and ask you for a commit message for the two commits you re squash ing together The default message looks like this This is a combination of t
107. erent areas of it Alice pushes her change back to their shared repository then Joe attempts to push his Joe s attempt will be rejected because Git detects that there has been a change on the server after he got his copy Joe has to pull those changes from the repository handle conflicts if there are any and then push his change back to the server This all sounds incredibly complex but it s pretty simple You rarely have two people on the same team editing the same file so this prob lem doesn t occur often When it does Git can handle most merges automatically 3 This is sometimes referred to as optimistic concurrency control in the computer science world Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 NEXT STEPS lt 25 nfiguration Man ment CM You might have heard of tools loosely called configuration management CM They are a class of tools designed to han dle the configuration of an application across multiple versions Many are built on top of a VCS and do support tracking the history of the configuration but they are not version control sys tems by themselves 1 10 Next Steps We ve taken a 30 000 foot view of the DVCS world and the way Git interacts with it We ve covered what repositories are determined what we should store nearly everything and talked about what working trees are You learned how files are tracked and how repositories stay in sync and
108. error patch failed index htm1 5 error index html patch does not apply Using index info to reconstruct a base tree Falling back to patching base and 3 way merge Auto merged index html CONFLICT content Merge conflict in index html Failed to merge in the changes Patch failed at 0001 When you have resolved this problem run git rebase continue If you would prefer to skip this patch instead run git rebase skip To restore the original branch and stop rebasing run git rebase abort Oops There s an error right off the bat Remember we covered handling conflicts in Section 5 4 Handling Conflicts on page 74 Using the git mergetool is the normal course to take here but editing by hand is going to be easier this time That s because there isn t a right or wrong change You want both the new paragraph from 1 0 1 and the unordered list that you added after creating the 1 0 tag Editing the file by hand is the easiest way here Your index html file has this conflict in it HEAD index html p lt li gt lt a href bio htm1 gt Biography lt a gt lt 1 i gt lt ul gt gt gt gt gt gt gt gt add in a bio link index html Remove the three lines that signify the conflict so it reads like a normal file After you save the file run the following to tell Git the conflict is resolved and to continue rebasing prompt git add index html Report erratum 0 printing March 2 R
109. es for example it will display a fatal error such as this Valid naming is discussed in Section 8 3 Using Valid Names for Tags and Branches on page 114 prompt git tag version 1 1 fatal version 1 1 is not a valid tag name Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 MARKING MILESTONES WITH TAGS lt 111 Git creates a tag based on the current working tree s commit if you call it and provide only a tag name You can provide it with an additional parameter to specify the commit you want to tag The extra parameter can be any valid commit or branch name For example you can create a tag from the latest commit in your con tacts branch by calling git tag like this prompt gt git tag contacts 1 1 contacts prompt gt git tag 1 0 1 1 contacts 1 1 You can use tags to return to the state of the repository that they marked Even though you can t make changes to a tag you can check it out like you would a branch prompt gt git checkout 1 0 Note moving to 1 0 which isn t a local branch If you want to create a new branch from this checkout you may do so now or later by using b with the checkout command again Example git checkout b new branch name HEAD is now at 4b53779 Add in a description element to the metadata At this point you re in a no man s land of sorts You re not on a branch so you can t track changes If you run git branch to see your
110. estions or corrections on the errata page At this point I m sure you re teeming with questions So without fur ther ado let s jump into it 3 http www pragprog com titles tsgit Report erratum h 2009 Prepared exclusively for Frode Nilsen Part I Welcome to the Distributed World Chapter Version Control the Git W A version control system VCS is a methodology or tool that helps you keep track of changes you make to the files in your project In its sim plest manual form a VCS is you creating a copy of the file you re work ing with and adding the date and time to the end of it Being pragmatic we want something that will help automate that pro cess This is where VCS tools come in They track all the changes for us keeping a copy of every change made to the code in our projects Distributed version control systems DVCSs are no different in that respect Their main goal is still to help us track changes we make to the projects we re working on The difference between VCSs and DVCSs is how developers communicate their changes to each other In this chapter well explore what a VCS is and how a DVCS Git in particular is different from the traditional centralized model You ll learn the following What a repository is How to determine what to store What working trees are How files are manipulated and how to stay in sync How to track projects directories and their files How to m
111. explain the commit like you would to a developer sitting right next to you Another way to handle commits is to pass git commit the a parameter on the command line It tells Git to take the most current version of your working tree and commit it to the repository It won t add new untracked files however only files that are already being tracked If the only change you had made to your working tree in the previous example was to some file you could perform the same commit by exe cuting the following prompt git commit m changes to some file a The last method of committing changes is to specify the file or files you want to commit Just add each file you want to commit after you specify all the options you want to pass Git Like the a parameter this takes the latest version from your working tree But it takes just the file or files you specify Here s an example from the two previous commits prompt git commit m changes to some file some file All three examples have their uses Staged commits are useful when you want to commit a portion of a file using the git add p command If you need to pull one file out of several that have changed and commit that you can commit using the explicit file Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 SEEING WHAT HAS CHANGED ing Git Ali Like SVN Shortcut If you re coming from Subversion you are probably used to alll Those shortcuts
112. few hundred more lines of output Now that Gitosis is installed you need to set up a user on your server that Gitosis can use To do that you have to create the credentials for your user 11 3 Creating Administrator Credentials You must create a SSH public key for your admin user on Gitosis A SSH public key is used by SSH to verify your connection instead of using a password If you already have a public key that you use with SSH you can use that now instead of creating a new one If not you will need to create a key Keys can be created from the command line by using the ssh keygen command You need this command on your local computer the one you use to connect to your server running Gitosis You can generate your key by running the following from the command line prompt ssh keygen t rsa The program will prompt you for the location where you want to store the new key The default location is fine so hit the Enter key to accept it It will then ask for your passphrase Your passphrase is required in order to use the key you are generating Just like a normal password choose this carefully and make sure you don t give it to anyone Report erratum Prepared exclusively for Frode Nilsen CONFIGURING THE SERVER FOR GITOSIS The ssh keygen program creates your key and gives you some informa tion about the new key If you left the location and name at their default values you now have a public key located in this
113. g March 2009 NETWORK PROTOCOLS lt 102 git github com tswicegood mysite chp6 git Protocol Server Repository Figure 7 2 Components of a git URL The major difference between this protocol and SSH besides encryp tion is that it is anonymous This is good if you want to provide public read only access to your repository but it can be dangerous if you open it up for writing you don t want just anyone changing your repository Almost every time you see a repository using git it will be read only It is common for repositories to utilize this protocol to allow other devel opers to pull their changes while using SSH to push their own changes into the repository to share HTTP HTTPS The HTTP protocol is generally considered the protocol of last resort It is the least efficient way to pull changes and requires much more net work overhead but it is almost always allowed by the strictest firewalls and is relatively quick and easy to set up Continuing with the example of mysite chp git on the github com server if GitHub had HTTP access to its repositories you would access GitHub with a URL like this http github com tswicegood mysite chp6 git GitHub doesn t support HTTP though so if you try to clone it you ll get an error from Git Choosing Networking Options With the git protocol SSH and HTTP HTTPS it may seem like there are a lot of choices to determine which networking option you should use C
114. g Release Branches 112 8 3 Using Valid Names for Tags and Branches 114 8 4 Tracking Multiple Projects 115 8 5 Using Git Submodules to Track External Repositories 116 9 Beyond the Basics 122 9 1 Compacting Repository History 123 9 2 Exporting Your Repository 4 124 9 3 Rebasinga Branch 4 44 640 064 840 ox a BSG 125 5 4 Using the Rhos 6 eee a m x 128 9 5 Bisecting Your Repository 131 III Administration 135 10 Migrating to Git 136 10 1 Communicating with SVN 136 10 2 Making Sure git svn Is Available 140 10 3 Importing a Subversion Repository 141 10 4 Keeping Up to Date with a Subversion Repository 143 10 5 Pushing Changes t SVN les 145 10 6 Importing trom CVS 6 4444 4406 bed dw oes 146 11 Running a Git Server with Gitosis 147 11 1 Making Sure Dependencies Are Met 148 11 2 Wistalling Gitesis lt oo c sec ee a wee eS 149 11 3 Creating Administrator Credentials 149 11 4 Configuring the Server for Gitosis 150 11 5 Inidalizig CHtoSES s soe ch mom mm mne 151 11 6 Configuring Gitosis a lt es e cestu naa eas 151 11 7 Adding New Repositories rss 152 11 8 Setting Up a Public Repository 154 11 9 Closing Thoughts as soea e RS Y AR 155 Report erratum Prepared exclusively for Frode Nilsen 2 0 printing N 2009
115. ge You use these commands doing normal day to day activities These are your bread and butter commands the ones we covered in Chapter 4 Adding and Committing Git Basics on page 51 Add a New File or Stage an Existing File and Commit prompt git add some file prompt git commit m some message gt Stage a Partial File Note indicates optional parameters prompt git add p some file gt some file gt and so on select hunks to commit Report erratum A 3 Add Files via Git s Interactive Add Mode prompt git add i Stage Changes to Modified Tracked Files prompt git add u some path some path gt Commit Changes to All Modified Tracked Files prompt git commit m some message gt a Revert Changes in a Working Tree prompt git checkout HEAD some file some file gt Reset Staged Changes That Haven t Been Committed prompt git reset HEAD some file lt some file gt Fix the Last Commit make whatever changes and stage them prompt git commit m some message amend Amend the Previous Commit and Reuse a Commit Message prompt git commit C HEAD amend Branches Branches are one of Git s strongest points This section covers com mands related to all aspects of branches You can find more details in Chapter 5 Understanding and Using Branches on page 65 Show Local Branches prompt git branch Show Just Remote
116. h to keep a copy of your code that s ready to release so you don t have to stop developing The command to create a branch is git branch and it takes two parameters the name of the branch you want to create and the name of the branch you want to create it from prompt git branch RB 1 0 master That command creates a branch called RB 1 0 from the master branch master is the name of the default branch in Git CVS and Subversion users might recognize this as the trunk in those VCSs The RB in the branch name stands for release branch Adding the prefix makes it easier for you and other developers to quickly determine what branches are release branches Now you can start making changes without affecting the code that s almost ready for a release Next up is adding a link to a bio page Right before the closing body tag add this lt ul gt lt li gt lt a href bio htm1 gt Biography lt a gt lt 1 i gt lt ul gt Commit your changes now except this time use the following com mand prompt gt git commit a editor launch create log message save and exit Created commit e993d25 add in a bio link 1 files changed 3 insertions 0 deletions Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 HANDLING RELEASES lt 44 Notice that this time the command has the a parameter on it That tells Git to commit all files that it knows about that have changed Now
117. has only one branch Just to tidy things up let s rename it to master prompt git branch m mymaster master Since everything is considered a branch in Git they re cheap Unlike other systems where all the files are copied into a new directory a branch in Git tracks the commits that were made to it from the point it was created Actually that s a little white lie Git s branches keep track of only the most recent commit to that branch That commit has a link to its par ent and using that link Git can figure out all the changes in that branch 1 Those with a background in computer science or mathematics might recognize this as a directed acyclic graph DAG Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 CREATING A NEW BRANCH One of the hardest parts of branches is figuring out when to create a branch It s an art not a science Here are a few of things that I create new branches for Experimental changes Want to try rewriting algorithms just to see whether they re faster or want to try refactoring a section of code to a particular pattern Create a new branch to do your work in and you can work on it separately from any changes that are being deployed immediately New features Every time you start working on a new feature cre ate a new branch You can merge it back in as soon as you re done either with the full history or through a squashed comm
118. hat was created from master and the search branch that was created from contacts The history of those branches might go something like this You started with contact code but partway into it you decide to add new search code too After you finish with the new search code you realize that it would work directly without requiring any of the changes that are in your contact branch This is what the onto parameter does It takes one parameter the branch you want to rebase onto Your command to rebase search onto the master branch looks like this prompt git rebase onto master contact search Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 USING THE REFLOG 44 128 This breaks the search branch off the contact branch and moves it to the master branch This is useful if you need to merge the search branch back into master but don t need everything in the contact branch Of course search has to be completely independent to keep from having any merge conflicts when the rebase starts replaying the changes You can do some other interesting things with onto and a combination of commit ranges like we discussed in Section 6 2 Specifying Revision Ranges on page 82 For example you can erase a revision by using git rebase To erase the commit two commits ago you can do this prompt git rebase onto HEADAA HEADA HEAD This rebases onto the commit that happened two commits prio
119. he latest version of the Komodo IDE from its website http www activestate com Products komodo ide Eclipse Git Plug In Eclipse is a popular cross browser IDE written in Java It has support for every major programming language and runs on any platform that Java runs on There is a Git plug in that allows you to use Git directly inside the IDE Features include the ability to commit amend commits view diffs and visualize the repository history graphically You can find more informa tion including download information on the project s wiki page http git or cz gitwiki EclipsePlugin TextMate Git Bundle TextMate bills itself as the missing editor for Mac OS X Its excellent support for scripting languages and ease of use make it popular with developers working on OS X There is a Git Bundle for TextMate that allows you to work with Git directly inside TextMate You can get the bundle and more information about how to install it from the project website on Gitorious http gitorious org projects git tmbundle VCSCommand Word of caution I m a Vim user I used MacVim for nearly all the writ ing of this book so this review might be slanted 2 TextMate Power Editing for the Mac Gra07 is also available from the Pragmatic Book shelf if you re interested in learning more about TextMate Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 THIRD PARTY TOOLS 4170 VCSC
120. hoosing one is straightforward though If you want speed above all else you want the git protocol If you value security above all else SSH is the protocol for you If you don t want to have to reconfigure restrictive firewalls HTTP or HTTPS is the way to go Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 CLONING A REMOTE REPOSITORY lt 103 Authentication is an issue The git protocol is anonymous so allowing a repository to be written using it means anyone can write to your repository SSH requires proper user permissions for your repository to work and HTTP HTTPS requires a working WebDAV server You re not locked into one protocol though You can mix and match protocols to get an optimal balance of speed and security For my personal Git repository I use a mixture of SSH and git To write to my server I use SSH keys for authenticating users and allow anony mous reads via the git protocol Though the configuration may sound complex it s made simple by a program called Gitosis which we ll cover in Chapter 11 Running a Git Server with Gitosis on page 147 7 2 Cloning a Remote Repository Sharing your work with other developers means you need a remote repository The easiest way to work with a remote repository is to clone an existing repository Cloning creates a local copy of the remote repository For projects that are already in progress this is the normal route b
121. ian in yourself and start thinking about revising the history of your repository 6 6 Undoing Changes Hindsight is 20 20 or so they say Working with your code is no excep tion You commit a change and then realize it had a password in it that you shouldn t be sharing In a centralized repository where every change is sent back to a main repository you are almost out of luck There are some hoops you can jump through if you have administrator access but it might well cor rupt data Git plans for this type of mistake however All your changes happen locally and are shared only when you push them to a public repository Since you re the only one who has to stay in sync you can rewrite your history as much as you want Dangers of Rewriting History Before we start a word of caution be careful how you use the com mands in this section if you use Git like you would a centralized reposi tory and push every commit back upstream Changing the history after you ve shared it can lead to major headaches when others try to sync against your changes All these commands except git revert which is covered in Section 6 6 Reverting Commits on page 93 change the history of your repository This is dangerous in a centralized repository How can the repository keep track of content when its commits move around are renamed or even disappear One of the values of completely distributed development is that you share only what is ready Mak
122. ifying Revision Ranges I have what I ve come to call a nonhistorian brain Specifics take a lot of work for me to remember I know the gist of American history but I can t tell you specific dates unless they ended up spawning a national holiday The same thing happens when I code I added that functionality last Monday or Tuesday I fixed that bug this morning Git has a lot of functionality for looking through its logs that way Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 Prepared exclusively for Frode Nilsen SPECIFYING REVISION RANGES lt 83 Git provides some other useful ways for filtering the commits that you see Say you want to look at commits only from the last five hours so you add since 5 hours Your command now looks like this prompt gt git log since 5 hours commit Obb3dfb752fa3c890ffc781fd6bd5dc5d34cd3be Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 11 06 47 2008 0500 add link to twitter Likewise you can skip the last five hours and view only those commits older than that by using before 5 hours prompt git log before 5 hours 1 commit 18f822eb1044761f59aebaf7739261042ae10392 Author Travis Swicegood development domain51 com Date Sat Oct 4 10 34 51 2008 0500 add contact page has primary and secondary email The since and before options can take most English ways of specify ing a
123. ilestone such as a public release or something much more routine like the point at which a bug was fixed in your repository Tags help you keep track of the history of your repository by assigning an easy to remember name to a certain revision Up next we ll cover branches the part of any VCS that gives you the ability to work in alternate existences 1 7 Creating Alternate Histories with Branches When I was a kid one of my favorite book series was the Choose Your Own Adventure series Readers of these books will remember the way they work You read a few pages and then make a choice Does Joe enter the dark cave If so turn to page 42 Or does Joe turn around and leave the forest If so turn to page 23 You can think of your repository like a book You can read it from start to finish to get the entire story of your project Branches are like the Choose Your Own Adventure books There are multiple ways the story could go each with a different history So how do these alternate histories fit into your work with a version control system Let s say you have a few ideas to rewrite a calendar component in your project I ve never worked on a project that got the calendar portion of the code right the first time but even if it s not the calendar there s always something on a project that can be done better with the benefit of hindsight To make these changes you need to get the rest of the team on board and then you have to track
124. illiance of Git Not only is Git a distributed version control system but it is a platform for building other applications that depend on a file system and can benefit from versioning More specifically Gitosis is a tool for managing a remote Git server and its repositories It does this by using a Git repository to store its configuration All you have to do if you need to update the configuration of the server is push that new configuration to the Gitosis repository It manages this by taking advantage of the hook scripts located in the git hooks directory Hook scripts execute at certain events such as before a commit the pre commit script or right after a commit post comrnit Gitosis uses these scripts to update the configuration files for the repos itories you create It handles things such as creating the empty reposi tory and who has access to read or write to the repository for you Gitosis is still a fairly new project so you have to get your hands a little dirty working under the hood to get it installed and configured The steps required to install Gitosis are as follows Making sure dependencies are met Installing Gitosis Configuring the server for Gitosis Creating administrator credentials Initializing Gitosis Configuring Gitosis Oar WN MAKING SURE DEPENDENCIES ARE MET lt 148 If you re not familiar with running daemons on your server this chapter might not be for you The topics we re c
125. ind multiple tools When it does it asks which tool you want to use prompt git mergetool Merging the files about html Normal merge conflict for about html local modified remote modified Hit return to start merge resolution tool opendiff git mergetool looks at the value of merge tool in your configuration then it scans your system for valid merge resolution tools Valid tools are kdiff3 tkdiff meld xxdiff emerge vimdiff gvimdiff ecmerge and opendiff In the previous session all I have to do is press the Enter key to start OS X s FileMerge Utility via opendiff You can see what it looks like in Figure 5 1 on the following page Each tool is a little different so a step by step guide is impossible but the overall result is the same Each conflicting change is displayed and you choose which one you want to use Git stages your changes for commit once you successfully resolve the conflicts Go ahead and commit your change Leave m off and Git will prepopulate your log message with a message describing what just happened prompt git commit Created commit f846762 Merge branch about2 into about 2 http kdiff3 sourceforge net 3 opendiff is part of Xcode from Apple that can be downloaded from http developer apple com tools Report erratum Prepared exclusively for Frode Nilsen DELETING BRANCHES eoo abouthtml about html LOCAL 11486 html work book mysi about html
126. is generates a list of files that can be staged In this case there s one file to add so type 1 and it will change to having an asterisk beside its name to signify that it s going to be staged Update gt gt 1 staged unstaged path i unchanged 1 1 index html Update gt gt Once you re ready to leave this mode you can press Enter to return to the main menu Update updated one path Commands s 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 quit 8 help What now gt Now checking the status again you can see that there s one change staged and nothing listed in the unstaged changes What now 1 staged unstaged path E 1 1 nothing index html Commands sx 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 quit 8 help What now You can use the revert functionality if you need to unstage a change It works just like the update we did a few paragraphs ago What now 3 staged unstaged path Js 1 1 nothing index html Revert 1 staged unstaged path 1 1 1 nothing index html Revert gt gt reverted one path Report erratum Prepared exclusively for Frode Nilser ADDING FILES lt 54 Commands sx 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 q it 8 help What now gt Running status will show that the changes have gone to unstaged now What now gt 1 staged unstaged path lis unchanged 1 1 index html
127. it We ll talk about these different merging strategies in Section 5 3 Merging Changes Between Branches on page 69 Bug fixes Whether it s a fix to a bug in code that hasn t been released or code that has already been tagged for a release you can create a branch to track your changes to that bug This gives you a lot of flexibility in how you merge it back into the rest of the code just like creating a branch for a new feature This is espe cially true if your bug fix is going to take some experimentation How you create and use your branches depends a lot on the project I used Git to track all the changes to this book and employed a pretty extensive branch strategy My beta branch contained the latest copy of the book with the content that was ready to ship and each chapter had its own branch New edits to the chapters happened in their own branch and then I merged those changes back in to the beta branch once they were ready I also employed a lot of temporary branches For example every time I fixed errata I would create an errata branch make the corrections merge the changes back in and delete the branch That gives you the high level view of branches and introduces you to some basics about them Now let s start creating new branches 5 2 Creating a New Branch Creating a new branch is a simple process You still use the git branch command except this time you give it the name of the new branch you want to create You c
128. it commit m rename to more appropriate name Created commit 9a23464 rename to more appropriate name 1 files changed 0 insertions 0 deletions rename index html gt hello html 100 Now that you ve renamed the index html file let s talk about copying files Copying Files or Not If you re used to Subversion you might find it odd that Git doesn t have a git co command for copying There s a reason Git doesn t need it Subversion s copy is mainly to let you create branches and tags Git provides you with the commands to handle both of those directly Git does track copied code though Report erratum Prepared exclusively for Frode Nilsen MANAGING FILES 4 63 That brings us to a point we haven t talked much about yet Git doesn t track files it tracks content like we talked about in Section 1 5 Track ing Projects Directories and Files on page 19 Git has a good reason for this Filenames are nothing more than meta data added to the content of files so they can be organized Git can figure out that name by asking the file system about it but what it cares about is the content that s stored inside files So how does this all apply to copying files Since Git tracks only con tent it can detect when the same content is duplicated across multiple commits without you having to explicitly tell it to copy You can view the copied code something we ll cover in Section 6 5 Following Content on page
129. it gui at the command prompt Some OS specific installers include context menu links to open git gui the name of the project in the folder you are at git gui provides an interface like that in Figure 2 4 on the next page to many of the commands we ll be discussing in this book We won t specifically be covering the GUI interface but if you prefer working with a GUI you can follow along relatively closely with the examples using git gui Although git gui provides you with an interface to perform operations such as committing changes it doesn t provide any interface for viewing the history of your repository gitk does that You can start it by running gitk at the command line from within your project s directory gitk displays the history of all the changes you make to your repository If you want to see how the branches relate to each other you can add the all parameter to view all branches instead of just the current one One final tool that is useful if you re running Mac OS X is GitX It s a gitk clone created by Pieter de Bie that is built specifically for the Mac environment It is hosted and available for download on its GitHub web page We mentioned the documentation earlier when you were installing Git Now let s cover how to access it 8 Tcl Tk is a cross platform GUI toolkit 9 http gibx frim nl Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 ACCESSING GIT S B
130. ith changes and then share them when they re something worth sharing or quietly delete them if the experiment didn t work out Branches and tags are an important part of working with Git There s an entire chapter Chapter 5 Understanding and Using Branches on page 65 that covers how to use both Most branches need to be merged with other branches to keep them up to date Up next we ll talk about how Git handles merging the branches together Merging In our Choose Your Own Adventure story Joe s path when we met him had two distinct routes into the cave or out of the forest Often the plot lines would come back together later in the book though MERGING 4 Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 22 He might start off going through the cave but end up on the banks of the same river that flowed alongside the forest that he left Sometimes the author runs out of places to send our hero Joe so he has to go down the same path but get there multiple ways Likewise having a couple or even dozens of branches is OK but their paths will sometimes need to come together This is where merging comes in Merging is taking two or more branches and combining their history into one Git goes about merging the same way you might It compares two sets of changes and tries to determine where changes occurred When changes happen in different parts of a file Git can merge them aut
131. l 56 delta 21 reused O delta 0 Receiving objects 100 56 56 5 92 KiB done Resolving deltas 100 21 21 done COMPACTING REPOSITORY HISTORY lt 123 9 1 Compacting Repository History Everything in life needs a little maintenance to work optimally Your car needs its oil changed your floors need sweeping and Git needs to have git gc run Git stores everything The problem with this is that it occasionally will have some leftover data that is no longer useful For example when you use the amend parameter on git commit to fix a commit Git remem bers the older revision too Or you delete an experimental branch using the git branch D and Git knows what was in that branch even though nothing references it any longer This is where git gc comes in Once a month or about every 100 or so commits it s a good idea to run git gc to tidy things up by optimizing the way Git stores its history internally It doesn t change the history only the way it is stored Running git gc with an empty repository won t hurt anything but it won t accomplish much either To give our examples some meat I m going to use the repository my book is stored in I hadn t run git gc on my book s repository for a few weeks when I started writing this section In those few weeks I had made quite a few additions along with 50 or so small commits fixing errata that had been reported by my great beta book readers Here s what the git
132. l commit with submodule 2 files changed 4 insertions 0 deletions create mode 100644 gitmodules create mode 160000 hocus Now your submodule is ready to share with other repositories Creating a clone of a repository with submodules is a little different so let s try it Cloning a Repository with Submodules A few extra steps are required to set up submodules on a freshly cloned repository Let s walk through it here First things first create a clone of the magic repository prompt cd work prompt git clone magic new magic Initialized empty Git repository in work new magic git prompt cd new magic prompt 1s hocus You can see that the hocus directory is there but it s empty if you look in it Running git submodule shows that it hasn t been initialized prompt git submodule 20cc9ddc65b5f3ea3b871480c1e64d8085db48457 hocus Report erratum red exclusively for Frode Nilsen USING GIT SUBMODULES TO TRACK EXTERNAL REPOSITORIES lt 119 Remember from the previous section that the minus sign as the first character shows that a submodule hasn t been initialized Run the git submodule init command to initialize it prompt gt git submodule init hocus Submodule hocus git github com tswicegood hocus git registered for path hocus The hocus directory is still empty though There s one more command required to pull the changes into your submodule git submodule update Just like the other git
133. le gt Figure 10 2 Common CVS commands in Git Report erratum Prepared exclusively for Frode Nilsen COMMUNICATING WITH SVN 139 Import Subversion Repository Subversion Your Git Repository Repository Treat Subversion as an Upstream Repository Subversion Your Git Repository Repository git svn rebase git svn dcommit Figure 10 3 Two options for migrating from Subversion EE C G P t A quick note before we start when reading this chapter you ll see ref erences to both git svn and git svn This is to differentiate between the package of git svn and the command that is executed There are two ways to migrate to Git from Subversion The first is to import all your history and move on to using Git as your main VCS The second keeps Subversion around and uses Git s ability to not only import changes from Subversion but also push changes back to it Both of these are outlined in Figure 10 3 Report erratum red exclusively for Frode Nilsen MAKING SURE GIT SVN IS AVAILABLE lt 140 10 2 Making Sure git svn Is Available Git has a tool called git svn that handles communication with a Subver sion repository Depending on how you installed Git you may already have git svn installed To determine whether you have it installed run git svn version prompt git svn version git svn version 1 6 0 2 svn 1 4 4 If your output look
134. location home username ssh id rsa pub Copy this file to your server You re going to be using it shortly when you initialize Gitosis 11 4 Configuring the Server for Gitosis Gitosis requires two things in order to run on your server It must have its own user on the server and a directory to store all your repositories Each operating system has a slightly different way for adding new users In most Linux distributions you can use the adduser command Gitosis needs a new user on the system Their home directory is where Gitosis stores its configuration values and its repositories You can specify the home directory on most Linux systems by adding home path to home The home path can be located anywhere on the system that you want The convention within Gitosis is to put it in srv example com git changing example com out for your domain but that isn t required You can name this user whatever you would like but I m going with git If you use something else substitute the username in the commands in the rest of this chapter with your username prompt sudo adduser shell bin sh group N disabled password N home srv example com git git For those familiar with adduser this command will be self explanatory It creates a user named git that has their home set to srv example com git disables logging in with a password adds a git group and sets their shell to bin sh With the user set up and cre
135. master branch Squashing Commits Feature branches are a common way to use branches in Git You create your new feature or maybe even fix a bug inside a branch and then create a squashed commit to merge the changes back They are squashed because Git takes all the history of one branch and compresses it into one commit in the other branch Be careful with squashed commits Most of the time you want to keep all the commits separate in your history If the changes of a branch represent one indi vidual change then it s a candidate for squashing These are helpful when you re creating a new feature or fixing a bug that requires some experimentation You don t need each commit tracing your experimentation you just need the final outcome You need to have something to merge in order to create a squashed commit Let s create a branch from the master branch called contact and check it out prompt git checkout b contact master Switched to a new branch contact Now add a file called contact html Add your email address to the file and then commit it prompt git add contact html prompt git commit m add contact file with email Created commit 5b4fc7b add contact file with email 1 files changed 15 insertions 0 deletions create mode 100644 contact html Now add a second email address so there are two ways to contact you and commit it separately prompt git commit m add secondary email a Created commit 2f30c
136. me of your repos itory For example if your repository were called web you would add this repo web That s the INI setting for creating the new section It tells the configu ration that everything that comes after it is part of that section Now you need to add a line that says daemon yes so git daemon knows this repository can be read Your new section should look like this repo web daemon yes That s all there is to the configuration step Commit your changes and push them to your server Now you need to set git daemon git daemon needs to be run as your git user that you created earlier The easiest way to do that is by using sudo u git to prefix your command Other than that the only parameter that git daemon needs is base path That tells it where to look for your repositories Following the configuration that we ve used so far this is located in srv example com repositories The actual command to run git daemon looks like this prompt gt sudo u git git daemon base path srv example com repositories Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 CLOSING THOUGHTS lt 155 You can test that this works by cloning one of your read only reposito ries Using the web repository the clone command is as follows prompt gt git clone git example com web git Now you re set The git daemon command that you executed will run only as long as that user is
137. mediately if you don t need to check the history prior to creating the branch prompt git branch reflog restored Ocb04ad prompt git checkout reflog restored Switched to branch reflog restored git gc which we talked about in Section 9 1 Compacting Repository History on page 123 will cause some older reflog entries to expire For example the commits we just restored are normally deleted after thirty days This can be changed by changing the gc reflogExpireUnreachable config setting Likewise normal reflog entries are expired after ninety days unless you change gc reflogExpire to something else That is to keep the reflog from getting too large Youll rarely need to use the reflog but when you do it can be a life saver Rewriting history can be dangerous and git reflog is a safety net to help keep you safe from yourself Report erratum Prepared exclusively for Frode Nilsen BISECTING YOUR REPOSITORY lt 131 good commit bad commit Figure 9 2 Repository with a known good commit and a known bad commit 9 5 Bisecting Your Repository Try as we might bugs still make it into the software we create We add unit tests have rigorous acceptance tests created with clients and think through the implications of what we are creating but all of these steps require perfection from humans in order to work Plan for the occasional bug All those tools can help you locate the bug but when they fail you can turn to
138. mit m add link to Twitter a Created commit 07950f4 add link to Twitter 1 files changed 4 insertions 0 deletions Now add that link to the blog back in and create a new commit for it prompt gt git commit m add link to blog a Created commit 6cOeebe add link to blog 1 files changed 4 insertions 0 deletions You re finished with the changes breaking the commit into two so call git rebase continue prompt git rebase continue Successfully rebased and updated refs heads master A quick check of the log shows that there are now two commits back where the squashed commit was Of course this wouldn t be Git if git rebase couldn t serve another func tion too It works with branches to keep them synced and move them around We ll talk about that functionality in Section 9 3 Rebasing a Branch on page 125 Now you ve seen how to work with the history and sometimes even rewrite it in Git These are extremely useful parts of Git but they aren t things you ll be using every day At least at first As you get more comfortable with concepts like rebasing your reposi tory you ll find more and more instances where you can use it So far we ve talked only about working with your local repository As you ll see in the next chapter working with remote repositories lets you share your work with others and get updates from them Report erratum 7 1 Chapter 7 Now we ve covered everything you n
139. modified hocus no changes added to commit use git add and or git commit a All you have to do now is add the hocus directory and commit the change That tells Git you want to track the submodule using the new commit prompt git add hocus prompt git commit m update commit to track in submodule Created commit fedf2bc update commit to track in submodule 1 files changed 1 insertions 1 deletions Check out the patch for that commit You ll see the changes that Git recorded Pay special attention when updating the commit that a sub module should track There are a few things to keep in mind when working with submodules Report erratum Prepared exclusively for Frode Nilsen 0 printing March 2 USING GIT SUBMODULES TO TRACK EXTERNAL REPOSITORIES Gotchas to Watch Out For with Submodules Make sure you don t include a trailing slash with calling git add Git currently translates that into a request to add all the files from that repository into your current local repository instead of updating the commit a submodule should track A quick check of git status prior to a commit will show when this mistake has been made Another thing to keep in mind is that git submodule update is destruc tive Running the update command will overwrite any changes you have in your submodule that have not been committed Be sure to double check your submodule s working tree for changes before running git submodule update
140. n make it into the release before it happens And that s the mechanics of release branches in Git The hard part is figuring out when to create the release branch It depends on your orga nization s development style If you re constantly adding new features creating a branch as soon as the product is feature complete might be a good idea however if your development process is a little bit slower you might be able to wait to create the release branch until a few days before the release Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 USING VALID NAMES FOR TAGS AND BRANCHES 4114 Getting the timing just right is an art Git s easy merging that we talked about in Section 5 3 Merging Changes Between Branches on page 69 means that if you branch too early keeping the two branches in sync will be a snap and if you realize you should have branched earlier create the branch from the commit where you should have branched at Release branches and tags can help you organize your repository The only thing you have to watch out for is how to name them Git is pretty permissive in what it allows but there are a few gotchas We ll cover those next 8 3 Using Valid Names for Tags and Branches Let s talk about valid names for tags and branches before we jump off into some specific types of organization you can employ in Git Git is pretty liberal in what you can do but there are a few things to
141. n agile approach Practices of an Agile Developer Working in the Real World Venkat Subramaniam and Andy Hunt 189 pages ISBN 0 9745140 8 X 29 95 Er http pragprog com titles pad in It Page after page of solid advice all tried and tested in the real world This book offers a collection of tips that show you what tools a successful team has to use and how to use them well You ll get hi M cu ip quick easy to follow advice on modern techniques and when they should be applied You need this t A Practical Guide to Successful Software Projects book if you re frustrated at lack of progress on your project you want to make yourself and your team more valuable you ve looked at methodologies such as Extreme Programming XP and felt they were too well extreme you ve looked at the Rational Unified Process RUP or CMM I methods and cringed at the learning curve and costs you need to get software out the door without excuses Ship It A Practical Guide to Successful Software Projects Jared Richardson and Will Gwaltney 200 pages ISBN 0 9745140 4 7 29 95 http pragprog comf titles prj It All Starts Here If you re programming in Ruby you need the PickAxe Book the definitive reference to the Ruby Programming language now in the revised 3rd Edition for Ruby 1 9 Programming Ruby 1 9 The Pickaxe for 1 The Pickaxe book named for the tool on the cover is the definitive r
142. n t say much Did it not work Was it too slow Say that You ll thank yourself in six months when you re trying to remember why you reverted that change Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 REWRITING HISTORY Resetting Changes Right as you hit the Enter key you realize you ve just committed a configuration file with your private password in it We ve all been there With a centralized VCS you have to ask the systems administrator to perform some magic to remove all traces of the commit Git assumes we make mistakes like this and allows us to reset the repository to the state we want git reset takes a commit name as its parameter It defaults to HEAD if you don t provide one You can use the and commit name modifiers to specify a revision HEAD would reset two commits while 540ecb7 3 would reset to three commits before 540ecb7 git reset updates the repository and stages the changes for you to com mit This is useful when you notice an error in your previous commit and want to fix it Add soft when you want to stage all the previous commits but not commit them This gives you a chance to modify the previous commit by adding to or taking away from it The final option is hard and it should be used with care It removes the commit from your repository and from your working tree It s the equivalent of a delete button on your repository with no undo Let
143. n the Linux section The only part that changes is the documentation I would advise against adding doc and install doc to the make commands because the depen dencies can be a bit overwhelming Regardless of how you install Git you can run git version from the command line once you re finished installing to verify that it is installed prompt git version git version 1 6 0 2 Installing on Windows Windows support has never been at the forefront of Git development because of its roots in the Linux kernel community With its growing popularity people have started work on making Git completely cross platform If youre running Windows you have a few options to get it up and running 4 http code google com p git osx installer 5 This is available for free from http developer apple com tools xcode or from the disks that came with your Mac Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 INSTALLING GIT Cygwin The official way to run Git in Windows is to use Cygwin a Linux emu lator This presents several issues to most Windows users not the least of which is getting Cygwin installed and running If Cygwin happens to be your thing Git is available as a binary package under Devel gt git Fast Version Control System You need to be sure to have a few other packages as well First openssh from the Net category is a must because Git uses Secure Shell SSH as the def
144. nal line Your output will have more information displayed The in this out put is my name along with the timestamp of the commit but I had to remove it to fit it on the page The first eight characters youll recognize as a short name The number before the content shows the line of text that is being displayed Lines 2 to 4 of the previous session lines 1 to 3 of the file all have the same commit name and lines 5 to 7 have another These signify the two commits that we ve made so far Report erratum Prepared exclusively for Frode Nilsen 0 printing March 2 FOLLOWING CONTENT lt 90 Now let s rerun the command but this time add the M parameter This tells git blame to detect lines that have moved or been copied around within the same file prompt git blame M original txt b87524b7 1 This is the first line b87524b7 C 2 This happens to be the second line b87524b7 3 And this it is the third and final line b87524b7 4 This is the first line b87524b7 5 This happens to be the second line b87524b7 6 And this it is the third and final line Now all the commit names are the same Because Git tracks content it realizes that it has more of the same content when it detects the repeating pattern Git can also track copies between files Let s copy the original txt file into a new file with an equally original name copy txt Now add and commit this file Now add C C to git
145. nces are 1 in 263 or 1 in 9 223 372 036 854 775 808 In American English that s nine quintillion two hundred twenty three quadrillion three hundred seventy two trillion thirty six billion eight hundred fifty four million seven hundred seventy five thousand and eight hundred and eight And yes did have to look that up These forty character hashes are kind of hard to remember though and many times they re unnecessarily long Most of the time the first seven or eight characters of a hash will be unique enough to match Throughout Git and this book you ll see shorter commit hashes used When Git uses smaller hashes it uses the first seven characters The second line in the git log output is the commit s author info the third is the date the commit was made and the final bit of information is the commit log message from the commit Report erratum Prepared exclusively for Frode Nilsen STARTING TO WORK WITH A PROJECT 3 3 Starting to Work with a Project Now you have our repository in place and you re already tracking your first file Next up you have to start dealing with changes The HTML is missing the head and title elements Add them Now your index html file should look like this lt html gt lt head gt lt title gt Hello World in Git lt title gt lt head gt lt body gt lt h1 gt Hello World lt h1 gt lt body gt lt html gt You know that your file changed and so does Gi
146. nch but not in the about2 branch because we created the branch before we made the sec ond commit Switch over to about2 You can refresh about html to see that the last entry isn t there prompt git checkout about2 Switched to branch about2 Add another name to about html on the same line where you added your last entry but this time make it something different Report erratum Prepared exclusively for Frode Nilsen HANDLING CONFLICTS 4 75 Once it s saved commit your new change prompt git commit m add EMCAScript to list a Created commit b84ffdc add EMCAScript to list 1 files changed 1 insertions 0 deletions Now you manufactured a conflict Of course most of the time you won t realize what has happened until later when Git complains as you try to merge Let s see this in action Start by switching back to about and then try merging about2 into it prompt git checkout about Switched to branch about prompt git merge about2 Auto merged about html CONFLICT content Merge conflict in about html Automatic merge failed fix conflicts and then commit the result Notice the CONFLICT line It tells us that there was a conflict in the about html file This is what my list from about html looks like now ul lt li gt Erlang lt 1i gt lt li gt Python lt 1i gt lt li gt Objective C li lt lt lt lt lt lt lt HEAD about html li Javascript li li EMCAScript
147. ne Orders 1 800 699 PROG 1 919 847 3884 Online Orders www pragprog com catalog Customer Service orders pragprog com Non English Versions translations pragprog com Pragmatic Teaching academic pragprog com Author Proposals proposals pragprog com
148. nstalling on Linux Each distribution of Linux uses one of the various package managers available Most distributions contain Git within their repositories but since it is new you may have to search through development or unsta ble packages to find it The only problem with these packages is that they tend to go out of date quite rapidly You need to have Git version 1 6 0 or greater to follow along with the examples in this book For example right now Ubuntu has the two packages you need to install Git git core and git doc However they re both on version 1 4 4 Instead of relying on the prebuilt version of Git in this case I recom mend downloading the latest release from Git s website and compiling it yourself To do this in Ubuntu you need to have the build essential package in stalled Git also has some dependencies that need to be met but they don t change often so you can use apt get to grab all the dependencies with the following command prompt sudo apt get build dep git core git doc That installs all the dependencies for the git core and git doc packages the same dependencies Git has when you re building from source Once the installation is completed you can build Git To do that you need to uncompress the archive you downloaded from the Git website and switch into the directory where it s located To build Git type the following command prompt make prefix usr local all doc That sets up Git to be in
149. nstead of telling Git about a new file though it now tells Git about a new change to track prompt git add index html prompt git status On branch master Changes to be committed use git reset HEAD file se to unstage modi fied index html k Gk In the git status command after you add the modified index html the header is now Changes to be committed instead of Changed but not up dated If you turned colors on the line with index html also changed from red to green Fire off a git commit command remembering to include the m with a commit message explaining why you made your change and you are set prompt git commit m add lt head gt and title to index m This allows for a more semantic document Created commit a5dacab add head and title to index 1 files changed 3 insertions 0 deletions Notice this time I used two m parameters Git accepts as many as you want to add and treats each one as a new paragraph A quick check of git log shows the message with two paragraphs prompt git log 1 commit a5dacabde5a622ce8ed1dlaalef165c46708502d Author Travis Swicegood lt development domain51 com gt Date Sun Sep 21 20 37 47 2008 0500 add head and title to index This allows for a more semantic document That also introduces a new parameter to git log the 1 You can change the number to limit the output of git log to the number of commits you want W
150. o read your log messages you need to make sure you re including all the information it expects There are tools that can read commit logs and update third party tools such as ticket tracking systems to show activity on tasks Adding S Color to Git s Output If you turned colors on in your configuration you probably noticed the color the first time you ran git status Unstaged modifications modifications that Git doesn t know what to do with appear in red Once you stage the changes with git add They will change to green Report erratum Prepared exclusively for Frode Nilsen PPR EG 2 0 printing Marc USING AND UNDERSTANDING BRANCHES 3 4 Using and Understanding Branches Branches are a way to maintain alternate histories of the project you re working on like we talked about in Section 1 7 Creating Alternate His tories with Branches on page 21 Alternate histories are great but how do we use them in a real project The honest answer is any way you want For our purposes though we ll narrow it down a bit Two types of branches are useful different versions of a project in different branches and topic branches that deal with a specific feature In this section we ll talk about the first kind of branches Your mysite code is almost ready to be released but it still needs to be signed off on by everyone involved In the meantime you can start working on the new features in the next version You can use a branc
151. objects 100 9 9 933 bytes done Total 9 delta 0 reused O delta 0 Unpacking objects 100 9 9 done To repos mysite git 5ef8232 d49d1e5 master gt master You can add dry run to this command when you want to see what changes would be pushed You can also specify the repository you want to push to just like git pull The syntax is the same git push repository refspec The repository can be any valid repository Any of the URLs we discussed Section 7 1 Network Protocols on page 100 will work as will any named repository that we ll talk about in Section 7 5 Adding New Remote Repositories on the following page 1 That s the default behavior you can configure a branch to push to another one but Im going to let you work that one out on your own since it s not a normal case Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 ADDING NEW REMOTE REPOSITORIES lt 106 Retrieving Push han It s not common but there might be a case where you need to let someone push changes into your private repository Or maybe you have to do it push changes between my private repositories in other virtual machines whenever I m testing code in multiple OSs If changes are pushed into your repository either by your self or by someone else those changes won t be reflected in your working tree This keeps someone else from overwrit ing changes you have in your working
152. od and end with swp I add swp to the gitignore and Git ignores all matching files add swp to gitignore file prompt git status On branch master Untracked files use git add lt file gt gitignore nothing added to commit but untracked files present use git add to track to include in what will be committed Now the swap file is gone and replaced with the new gitignore It s a regular file that can be tracked and distributed with your repository so everyone who clones your work will ignore those files as well Every developer has their own favorite editor though and each one uses a different mechanism to save backups and signify that it has a file open Distributing your personal preferences as part of the repository might not be such a good idea You can tell your local repository to ignore files like these without shar ing the exclusion with everyone else Edit the file git info exclude and add your rules there Deciding Where to Ignore You can decide what to ignore at the repository level through gitignore and what to ignore locally through git info exclude by asking yourself a simple question Is this kind of file something that everyone is going to have in their repositories If the answer to that is yes you need to ignore it by adding the rule to the gitignore file and committing that file to the repository If it s only a file you ll see add it to your git info exclude fil
153. oint don t worry you can always clone the repository to get the repository that I built prompt git clone git github com tswicegood mysite git Initialized empty Git repository in work mysite git remote Counting objects 12 done remote Compressing objects 100 8 8 done remote Total 12 delta 2 reused O delta 0 Receiving objects 100 12 12 done Resolving deltas 100 2 2 done Now that you have your repository either the one you created in the previous chapter or by cloning mine yourre ready to start ADDING FILES 4 52 4 1 Adding Files You re constantly adding new files and making changes to your reposi tory s contents git add fills both of these roles Just give it the name ofa file or the files you want to add and Git stages the changes to commit Before we proceed there is a little terminology to clear up Staged changes are simply changes in your working tree that you want to tell your repository about When you stage a change it updates what Git refers to as its index A lot of people myself included refer to it as the staging area The staging area is just that a place where you can set up commits prior to committing to your repository But isn t this double the amount of work Why can t I just commit In a lot of cases yes it is double work and there are shortcuts that we ll talk about in the next section to get around it but don t forget about the staging are
154. omatically Sometimes it can t work out what was supposed to hap pen so it errs on the side of caution and tells you there s a conflict Say you and another developer on your team modify the same line of code but in different ways Git sees this and can t programmatically determine which one is correct so it flags them as a conflict and waits for you to tell it which change is correct Fortunately Git has several methods of handling conflicts Knowing how these work is an important part of mastering Git We ll cover all of the tools you can use in Section 5 4 Handling Conflicts on page 74 With all these branches floating around and all of this talk of merging you might be thinking How can I keep track of what I ve merged and where Thankfully you don t have to keep track Git handles it through merge tracking Just like it sounds merge tracking keeps track of what com mits have been merged together and doesn t merge them again This is a feature not found in many traditional VCSs such as CVS and until recently Subversion Without some sort of merge tracking you have to manually keep track of what commits have been merged and where Manually tracking merges adds to the overhead of branches and is one reason many developers have tried to avoid it in the past 2 Subversion 1 5 0 which was released in June 2008 now has merge tracking MERGING Report erratum Prepared exclusively for Frode Nilsen 22 0 printing
155. ommand is a plug in for the wildly popular and battle tested Vim editor Combine it with a few shortcuts in your vimrc file and you re set to take on the most challenging programming projects on any platform Too over the top OK Ill back it down a notch Vim is an editor that has been ported to every major platform It s even available on a jailbroken iPhone Vim or its predecessor vi is available on nearly every Linux box so there s a good chance it s available when editing code on a Linux box VCSCommand lets you interact with several VCS directly through Vim It currently supports CVS Subversion and Git It s written in Python so it requires the Python bindings for Vim You can get more information about VCSCommand from its listing on the Vim Scripts site http www vim org scripts script php script id 90 GitNub GitNub describes itself as a gitk like tool that looks like it belongs on a Mac It provides basic viewing of history and has integration with GitHub s timeline viewer if your repository is hosted on GitHub You have to build GitNub from source It requires Ruby and RubyCocoa along with Leopard You can get more information and the URL to clone it from its listing on GitHub http github com Caged gitnub TicGit Ticket tracking systems are how many teams keep track of who is work ing on what These introduce a centralized system into your distributed tool set TicGit lets you disconnect again with a simple di
156. ompt git clone git github com tswicegood mysite chp4 git Initialized empty Git repository in work mysite chp4 git WHAT ARE BRANCHES 5 1 What Are Branches We all have competing priorities at work that we have to juggle Adding new features refactoring existing code to make it more maintainable and fixing the occasional bug they all jockey for our attention and we have to balance them A straight linear history has a hard time coping with these demands This is where branches come in We talked about them in Section 1 7 Creating Alternate Histories with Branches on page 21 They allow you to track changes with different histories Here is Git s secret everything is treated like a branch So far all the work you ve been doing has been in the master branch but nothing is stopping you from giving it another name Actually let s do that prompt git branch m master mymaster prompt git branch mymaster That s it You renamed the master branch to mymaster Both of the com mands use git branch but they provide different parameters The first has three parameters The m parameter tells Git to perform a move The other two parameters are the old branch name and the new name you want your branch to have The second command is git branch by itself Git displays the names of all the local branches in your repository when it isn t given any param eters Git just shows the one branch name here since this repository
157. ompt python c import setuptools There is no output if EasyInstall and its setuptools module are avail able If you get a warning similar to the following one you will need to install EasyInstall Check your operation system s documentation for information on how to install EasyInstall or follow the instructions on its website prompt python c import setuptools Traceback most recent call last File stdin line 1 in module ImportError No module named setuptools 1 http peak telecommunity com DevCenter Easylnstall Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 INSTALLING GITOSIS lt 149 11 2 Installing Gitosis Gitosis is still in active development so you have to install it from its source code You can get its source code directly from its Git repository by cloning it prompt git clone git eagain net gitosis Initialized empty Git repository in work gitosis git remote Counting objects 599 done remote Compressing objects 100 168 168 done remote Total 599 delta 422 reused 599 delta 422 Receiving objects 100 599 599 92 57 KiB 59 KiB s done Resolving deltas 10096 422 422 done Now you have a copy of the source code located in the gitosis directory To install Gitosis change into that directory and run the setup py file like this prompt cd gitosis prompt sudo python setup py install running install a
158. on Author Pragmatic Version Control Using Subversion Pragmatic Version Control Using Git Travis Swicegood The Pragmatic Bookshelf Raleigh North Carolina Dallas Texas t matic ookshelf Many of the designations used by manufacturers and sellers to distinguish their prod ucts are claimed as trademarks Where those designations appear in this book and The Pragmatic Programmers LLC was aware of a trademark claim the designations have been printed in initial capital letters or in all capitals The Pragmatic Starter Kit The Pragmatic Programmer Pragmatic Programming Pragmatic Bookshelf and the linking g device are trademarks of The Pragmatic Programmers LLC Every precaution was taken in the preparation of this book However the publisher assumes no responsibility for errors or omissions or for damages that may result from the use of information including program listings contained herein Our Pragmatic courses workshops and other products can help you and your team create better software and have more fun For more information as well as the latest Pragmatic titles please visit us at http www pragprog com Copyright 2008 Travis Swicegood All rights reserved No part of this publication may be reproduced stored in a retrieval system or transmit ted in any form or by any means electronic mechanical photocopying recording or otherwise without the prior consent of the publisher Printed in the
159. one willing to answer questions from basic to advanced From time to time I m also on the IRC channel I m the ever creatively named tswicegood so say Hi if you see me in the channel Pragmatic Version Control Using Git Forums Lastly I would be remiss if I didn t mention the book s forums http forums pragprog com forums 64 I keep an eye on the forums regularly and though most of the discus sion so far has been related to the book I hope they turn into a place where people can come for help when they re looking to answers to their Git questions Report erratum Prepared exclusively for Frode Nilsen FBB 99 Fri97 GraO7 Hun08 SHO6 Appendix C Bibliograph Martin Fowler Kent Beck John Brant William Opdyke and Don Roberts Refactoring Improving the Design of Existing Code Addison Wesley Longman Reading MA 1999 Jeffrey E F Friedl Mastering Regular Expressions O Reilly amp Associates Inc Sebastopol CA 1997 James Edward Gray II TextMate Power Editing for the Mac The Pragmatic Programmers LLC Raleigh NC and Dallas TX 2007 Andy Hunt Pragmatic Thinking amp Learning Refactor Your Wetware The Pragmatic Programmers LLC Raleigh NC and Dallas TX 2008 Venkat Subramaniam and Andy Hunt Practices of an Agile Developer Working in the Real World The Pragmatic Pro grammers LLC Raleigh NC and Dallas TX 2006 A Adding files 52 56 Adding remot
160. or an old hand you ll find tips to make your day easier This is the Linux book for the rest of us 4 Keir Thomas tect vyso Corer Ubuntu Kung Fu Tips Tricks Hints and Hacks Keir Thomas 400 pages ISBN 978 1 9343562 2 7 34 95 http pragprog com titles ktuk The Pragmatic Bookshelf The Pragmatic Bookshelf features books written by developers for developers The titles continue the well known Pragmatic Programmer style and continue to garner awards and rave reviews As development gets more and more difficult the Pragmatic Programmers will be there with more titles and products to help you stay on top of your game Visit Us Online Pragmatic Version Control Using Git s Home Page http pragprog com titles tsgit Source code from this book errata and other resources Come give us feedback too Register for Updates http pragprog com updates Be notified when updates and new books become available Join the Community http pragprog com community Read our weblogs join our online discussions participate in our mailing list interact with our wiki and benefit from the experience of other Pragmatic Programmers New and Noteworthy http pragprog com news Check out the latest pragmatic developments in the news Duy the Book If you liked this PDF perhaps you d like to have a paper copy of the book It s available for purchase at our store pragprog com titles tsgit __ContactUs 0 0 0 0 Pho
161. ory Cloning makes a copy of another repository and then checks out a copy of its master branch its main line of development Checking out is the process Git uses to change your working tree to match a certain point in the repository We ll talk more about cloning repositories in Section 7 2 Cloning a Remote Repository on page 103 Of course a VCS is all about tracking changes So far we ve talked about repositories and your working tree your current view of the repository but we haven t talked about those changes yet Now we ll cover that 1 4 Manipulating Files and Staying in Sync Tracking changes to your files over time is the whole reason for using a VCS You make changes to the source code rerun your unit tests to make sure your changes don t have any side effects and then commit those changes Committing a change adds a new revision to the repository and stores your log message explaining what the change did This gives you a record to go back through if you ever need to figure out why a certain change was made or when a bug was introduced Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 TRACKING PROJECTS DIRECTORIES AND FILES A DVCS such as Git requires that you share your changes with other developers in order for them to have access to them This is done by pushing the changes to an upstream repository An upstream repository is a public repository that you and possibly
162. ory as content This is different from many version control systems that track files Instead of tracking a models py file Git tracks the content the individual characters and lines that make up the variables functions and so on of models py and Git adds metadata to it such as the name file mode and whether the file is a symlink It S a nuanced difference but it s an important one Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 TRACKING MILESTONES WITH TAGS Technically this has a lot of advantages It reduces the amount of stor age space needed to store the entire history of your repository and makes it feasible and fast to do things such as detecting functions or classes moving between two files or determining where copied code came from We ll cover this in more detail in Section 6 5 Following Con tent on page 88 You interact with the data in those files exactly like you do any other files All your work happens in the working tree It s a set of normal directories and files that represents your current view of the repository The way you organize the files and directories in your repository makes up your project Most projects follow a specific structure so everyone on the team knows where to put files so everyone else can find them Most companies however have more than one project Some larger projects might even be broken down into several modules to make them more manag
163. ory using git log Specify ranges of commits to help searching View differences between commits Annotate files with a line by line history Follow content as you move it around Undo changes you ve made Rewrite the history of your repository Inspecting that history can provide invaluable information Why does this file not conform to our coding standard A quick check of a file s log might show that it has not been touched since it was originally hacked together with a log message of moke ready for client demo If your questions are more specific Git can show you an annotated version of your file that tells you who changed each line and when You can drill down further to show the differences between two revisions of a file Finally Git lets you rewrite the history of your repository in several ways but be careful or the other members on your team might quit talking to you after they spend a morning trying to fix broken merges INSPECTING GIT S LOG lt 4 81 In this chapter you ll learn how to deal with all these tasks we ll start with looking at where we ve been by learning about git log This chapter uses the repository you ve been working on throughout the book If you don t have a copy and want to follow along with the examples in this chapter you can clone the repository from GitHub prompt git clone git github com tswicegood mysite chp5 git Initialized empty Git repository in work mysite chp5 git remote
164. overing although straightfor ward fall to the more complex end of the spectrum Don t fret if setting up servers isn t your thing you have a couple of op tions You can try to enlist the help of a sysadmin buddy by bribing err paying him to help you out This chapter will make perfect sense to him Or if your social circle is lacking anyone who can work their sysadmin magic for you you can also look to external hosting services GitHub and Gitorious both offer free hosting I talk more about these in Sec tion B 3 Git Repository Hosting on page 171 11 1 Making Sure Dependencies Are Met Gitosis has a few dependencies First since it is written in Python you will need to have that installed on your system Python is pretty popular so it may already be installed on your system The easiest way to check is to run the following command from the command prompt prompt gt python version Python 2 5 1 If Python is installed on your system you will get a response similar to the one shown here but the version number may be different depend ing on which version of Python you have installed You also need the EasyInstall package from the Python Enterprise Application Kit PEAK EasyInstall is a package that helps develop ers install Python based applications and handle dependencies It is a popular package so you may already have it installed on your system You can check by running the following from the command line pr
165. ow you need to clone Gitosis s configuration repository It contains all the configuration values you need to manage your new repositories You must clone it from the computer where you generated the SSH public key That s the only one that Gitosis knows about right now If your server s domain name was example com your clone command would look something like this prompt git clone gitQGexample com gitosis admin git Initialized empty Git repository in work gitosis admin git remote Counting objects 5 done remote Compressing objects 100 4 4 done remote Total 5 delta 1 reused 5 delta 1 Receiving objects 100 5 5 done Resolving deltas 100 1 1 done There is a gitosis conf file and a keydir directory in your newly cloned repository Report erratum Prepared exclusively for Frode Nilsen ADDING NEW REPOSITORIES gitosis conf is a simple INI style file Its sections are denoted by brackets and its values have a name an and the value The default configu ration looks something like this gitosis group gitosis admin writable gitosis admin members travis The part that s interesting here is the block after group gitosis admin The first line specifies that this group can write to the gitosis admin repository The second line specifies the users or in this case the user that are part of this group The members field is a space separated field Each entry refers to a file in
166. pository hosting service You can try the git clone command by creating a clone of it prompt cd work prompt git clone git github com tswicegood mysite git mysite remote Initialized empty Git repository in work mysite remote git remote Counting objects 12 done remote Compressing objects 100 8 8 done remote Total 12 delta 2 reused O delta 0 Receiving objects 100 12 12 done Resolving deltas 100 2 2 done git clone takes two parameters the location of the repository you want to clone and the directory where you want the repository to live The second is optional but you already have a mysite directory so you need to provide the second parameter to put it in a directory of its own That s all there is to cloning You can provide some additional param eters that we ll talk about in Section 7 2 Cloning a Remote Repository on page 103 but the majority of times you create a clone providing the location and the directory you want to store the clone in is all you need to do Of course you can push and fetch changes as well We re going to save those for later though once you re more comfortable working with your local repository There s a whole chapter Chapter 7 Working with Remote Repositories on page 100 devoted to working with remote repositories Are you dizzy yet In this chapter you learned the basics of Git git add git commit git status and git log We built on that foundation
167. r prompt gt cd mysite chp6 prompt 1s about htm1 contact html copy txt hello htm original txt You now have a fully functioning clone of the remote repository that is set up to track both your own local changes and those you fetch from the remote server 7 3 Keeping Up to Date Cloning gets you the history of a repository up to the point you clone it but other developers will still be making changes and updating the repository with those changes after you clone it You need to fetch those changes from the remote repository You do this by using the git fetch command Fetching changes updates your remote branches You can see your local branches when you run git branch If you add the r parameter Git shows you the remote branches prompt git branch r origin HEAD origin master You can check out those branches like a normal branch but you should not change them If you want to make a change to them create a local branch from them first and then make your change Running git fetch updates your remote branches it doesn t merge the changes into your local branch You can use git pull if you want to fetch the changes from a remote repository and merge them into your local branch at the same time git pull takes two parameters the remote repository you want to pull from and the branch you want to pull without the origin prefix Speaking of the origin prefix in the remote branch name that s to keep the remote branches
168. r to your current HEAD starting one commit ago through the current HEAD Of course any time you start rewriting the history of a branch it s a good idea to have a backup plan in case things go wrong You can create additional branches to experiment in before you do them in your live branches Since branches are so cheap in Git it s a good idea to use them instead of live branches when you experiment with rebasing There is another tool that comes in handy if things go wrong the reflog 9 4 Using the Reflog One of the key tenets that Linus set for Git was that it had to be safe Being nondestructive means you have to be able to get back to any state in the repository and to do that you need to have some mechanism for tracking the changes in state The normal history of a repository will protect you in all but the most extreme cases with a normal version control system Git allows you to do things that most VCSs can t Changing the order of commits breaking one commit into multiple commits removing commits adding extra ones these are all tasks that Git does that a VCS like Subversion or CVS can t Of course with all this power comes some risk What happens when you accidentally delete a branch using git branch D or a git rebase i goes wrong This is where Git s reflog comes in 1 This happened to your humble author the first time he did an interactive rebase About fifty commits disappeared in about five seconds and wer
169. race bugs quickly The enterprising development team could even tie it into their auto mated build system to help isolate bugs This can be a tremendous time saver when a project moves too rapidly to be tested with a tra ditional continuous integration system where each change kicks off a new build This brings us to the end of the basics chapter and the end of Part II Whether you ve just started your journey as a developer and are learning your first VCS or you are an old hand looking to pick up Git you now know what you need to start being productive with Git Part III covers administrative tasks It s required reading only if you plan on migrating to Git from Subversion or CVS covered in Chap ter 10 Migrating to Git on page 136 or are going to set up your own remote repository covered in Chapter 11 Running a Git Server with Gitosis on page 147 Report erratum h 2009 Prepared exclusively for Frode Nilsen Part III Administration 135 10 1 Chapter 10 If you ve been developing for long you probably have a Subversion or CVS repository that already has your complete project history stored in it Switching to Git doesn t mean you have to lose all that history In fact Git provides several tools to make migrating easy In this chapter you ll learn how to do the following Import your history from Subversion Stay in sync with a remote Subversion mport your history from CVS To help you map th
170. rch 2009 10 3 IMPORTING A SUBVERSION REPOSITORY Being th it Usin it in version mpan At a past job worked on performance testing and tuning of the company s application did a lot of experimentation interspersed with random adjustments to specific areas as they came across my radar The engineering department used Sub version to track their changes My development was anything but linear often worked on several different areas during the course of a week The central ized model with expensive branches and lack of merge track ing didn t work well for me Git s cheap branches allowed me to work much more effec tively without the mental and physical overhead of maintaining separate copies of the half dozen or so branches had There s another benefit Following the advice in Practices of an Agile Developer SHO6 Git allowed me to share work only when it was ready If not ran the risk of someone seeing some partially completely algorithm change and thinking Well if Travis did it this way it must be good By using Git could manage multiple branches of code keep ing them all current without manually tracking merges craft ihe commits wanted to push back to our main repository and commit new code only once it had been proven as more efficient If you re on a Mac the MacPorts package is called subversion perlbindings prompt sudo port install subversion perlbindings If you use CPAN to keep your Pe
171. re multiple projects with one repository This requires a little more setup but allows each project to have its own independent history Determining when to split a project is a straightforward process Flip the rule on keeping all projects in one repository Will this project be released by itself If it will it needs to be in its own repository This isn t a rule set in stone If you release the two projects indepen dently but they are so coupled that you can t use one without the other sometimes it is more convenient to have them in one repository so you have to clone only the one Like everything in Git there is yet another way to handle this situation That brings us to our next topic Git submodules 8 5 Using Git Submodules to Track External Repositories Sometimes you need to track multiple repositories as if they re all in the same repository This might be because of a dependency on some third party library or possibly because your in house project has been divided into multiple projects to help make them more manageable Git allows you to track external repositories through what it calls sub modules These allow you to store a repository within another repository while keeping the two histories completely independent Those coming from a Subversion background might recognize these as svn externals Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 USING GIT SUBMODULES TO TRACK EXTER
172. repository local branch Push Local Changes to Origin Repository This pushes only those branches that are already present in the origin repository To push a new branch you must use the git push repository name local branch syntax prompt git push Delete a Remote Branch prompt git push remote repository remote branch Remove Any Stale Remote Branches prompt git remote prune remote repository Remove a Remote Repository and Any Associated Branches prompt git remote rm remote repository A 6 Gitto SVN Bridge The ability to receive and send commits to and from a Subversion repos itory is one of the many finishing touches that sets Git apart from all the other DVCSs These are a few of the more common commands used when working with a remote SVN repository You can find out more about them in Chapter 10 Migrating to Git on page 136 Clone an Entire SVN Repository prompt git svn clone svn repository Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 GIT TO SVN BRIDGE 44 166 Clone an Entire SVN Repository Using Standard Layout Use this if you are cloning a repository that uses the standard trunk branches and tags repository structure prompt git svn clone s svn repository Clone an Entire SVN Repository with Nonstandard Layout prompt git svn clone T trunk path b branch path t tag path svn repo
173. reverts a commit by creating a new commit in your repository that reverses all the changes made by the original commit Normally Git commits the reversal immediately but you can add the n parameter to tell Git not to commit This is useful when you need to revert multiple commits Just run multiple git revert commands with the n parameter and Git stages all the changes and waits for you to commit them You must provide it with a commit name so it knows what to revert For example if you wanted to revert the commit 540ecb7 and HEAD use the following Always revert backward the most recent first That makes sure you don t have any unnecessary conflicts to work through when reverting multiple commits prompt git revert n HEAD Finished one revert prompt git revert n 540ecb7 Removed copy txt Finished one revert prompt git commit m revert 45eaf98 and 540ecb7 Created commit 2b3clde revert 45eaf98 and 540ecb7 2 files changed 0 insertions 10 deletions delete mode 100644 copy txt By default git revert starts up your editor for your commit message The default message is added to the editor Revert your original log mes sage followed by the text This reverts commit commit name You can add no edit to git revert when you want it to use the default message Just like any other commit make sure you explain why you re making this commit Just marking that you re reverting a change like I did here does
174. rl libraries up to date you can also install the package directly through it The package you want to install is SVN Core prompt sudo cpan install SVN Core Importing a Subversion Repository To import a Subversion repository s history into Git use the git svn clone command to Just like its normal Git counterpart git svn clone retrieves the entire history of a repository and stores it in your repository Report erratum Prepared exclusively for Frode Nilsen P2 0 printing March 2009 IMPORTING A SUBVERSION REPOSITORY Beware of CPAN on M spent two afternoons trying to figure out why MacPorts was telling me had everything needed but Git wouldn t recognize it It turns out had two versions of the Perl Subversion bindings on my system an outdated one that was installed by Subver sion when originally set it up on my machine and the newer one on MacPorts To make matters worse before I realized what had happened had also installed it via CPAN so now had three versions installed My CPAN one worked but when pointed Git to it another dependency failed Once realized that my CPAN library didn t have all the dependencies met it was a quick fix but it still took a few hours that wish had back You do have to tell Git how the repository is structured If you follow the recommended Subversion repository layout you can provide the s That tells Git to utilize the standard layout You can us
175. roject that is made up of several components that are all released together It could be a CMS an order entry system or any other type of program that consists of several distinct components that are all released at one time as a package Notice that I keep talking about releasing at the same time This is the criteria I use for determining whether a repository should contain one or multiple projects like we ll discuss in Section 8 4 Multiple Projects Multiple Repositories on the following page If each smaller project or component is only ever released as part of the larger project then sharing the same history might be a good idea Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 USING GIT SUBMODULES TO TRACK EXTERNAL REPOSITORIES This makes sure that all the history in the repository revolves around one project If they are released separately then they probably need their own his tory The distinction is made because of the way tags and branches are handled within Git They refer to the whole repository not one section of it With multiple projects on independent release schedules the number of branches and tags you have to create will increase exponentially Repositories are lightweight in Git though so creating one repository for each project isn t difficult Multiple Projects Multiple Repositories Creating one repository per project is the alternative to trying to sto
176. rom Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 REWRITING HISTORY 4 96 In this case we want HEAD 3 prompt git rebase i HEAD 3 launches configured editor pick 222cb82 adding copied lines to showcase git blame pick 540ecb7 copy original to show cross file blame pick 45eaf98 add link to blog Rebase b87524b 45eaf98 onto b87524b Commands p pick use commit e edit use commit but stop for amending Ss squash use commit but meld into previous commit If you remove a line here THAT COMMIT WILL BE LOST However if you remove everything the rebase will be aborted 2 Everything in the editor that begins with a is a comment and is ignored by Git The first three lines are the three commits we re working with Move the pick 45eaf98 line to the top line Now the first three lines look like this pick 45eaf98 add link to blog pick 222cb82 adding copied lines to showcase git blame pick 540ecb7 copy original to show cross file blame Save the editor s contents and exit then Git starts the rebase operation When it s finished you can rerun the git log command to see the new order prompt git log pretty format h s HEAD 3 8c764d3 copy original to show cross file blame be53bab adding copied lines to showcase git blame 4f7621d add link to blog Squashing Multiple Commits into One There is one more thing you can do h
177. ry prompt git log stat Show Status of Files Touched by a Commit prompt git log name status Show the Differences Between the Current Working Tree and the Index prompt git diff Show the Differences Between the Index and the Repository prompt git diff cached Show the Differences Between the Working Tree and the Repository prompt git diff HEAD Show the Differences Between the Working Tree and the Previous Point in Repository start point can be a commit branch or tag name prompt git diff start point Show the Differences Between Two Points in a Repository prompt git diff start point end point Show Stats from Differences prompt git diff stat start point end point gt Annotate a File with Commit Information prompt git blame some file gt Annotate File and Show Copy and Paste and Line Movement Within File prompt git blame M some file Annotate File Show Line Movement and Original File prompt git blame C C some file gt Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 E 163 REMOTE REPOSITORIES Show Copy and Paste Within the Log prompt gt git log C C p 1 lt some point gt A 5 Remote Repositories You collaborate with other developers by using remote repositories to share your work and interact with others work This section covers those commands many of which are covered in Chapter
178. s ECLIPSE GIT PLUG IN p GIT GUI E Eclipse Git plug in 169 Empty directories 56 Errors 144 Exporting repository 124 125 F Feature branches 70 Fetching remote repositories 104 105 Files adding 52 56 committing 55 58 copying 62 differences between 60 hunks 54 ignoring 63 64 managing 61 64 manipulation of 18 19 status and history of 58 61 Fink 26 Go Git branches 22 built in help for 34 35 commands in 122 configuration of 31 33 conventions 13 development of 10 forums for 173 GUI 33 34f hashes in 39 installation of 30f 31f 26 31 32f merging 23 migrating to 136 146 git svn 140 142 CVS commands in 138f importing from CVS 146 importing from Subversion 141 144 pushing to Subversion 145 Subversion commands in 137f SVN communication 139f 136 139 tracking changes from Subversion 143 145 network protocols 101f 102f 100 103 protocol for 101 pulling 19 pushing 17 setup of 158 strengths of 10 submodules 116 121 URL components 101 102f user manual 172 website for 172 see also Gitosis git 13 git add 52 57 62 127 git archive 47 124 125 git bisect 131 132 134 git blame 86 89 90 git branch 43 66 68 77 110 111 113 130 git checkout 45 68 121 git checkout HEAD 106 git cherry pick 72 73 git clone 48 103 git commit 56 58 92 git config 58 git daemon 154 155 git diff GO 85 86 8
179. s Book This book is divided into four parts e Part Iis an introduction to version control with a Git slant Chap ter 1 Version Control the Git Way on page 15 is where you ll learn about version control in general and some of the fundamental con cepts around VCS and how DVCS is different Chapter 2 Setting Up Git on page 26 walks you through installing and configuring Git and Chapter 3 Creating Your First Project on page 36 gets your feet wet by working on a simple HTML project that showcases a lot of Git s functionality in a real project Chapters 2 and 3 are hands on so have your computer handy Part II is where the training wheels come off Chapter 4 Adding and Committing Git Basics on page 51 deals with the basics the commands you need to accomplish everyday tasks getting a repository started making commits and so on Next up we jump into branches in Chapter 5 Understanding and Using Branches on page 65 Branching is so key to how Git oper 2 Don t worry if you don t know HTML our project is a simple one Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 WHAT S IN THIS BOOK ates that there s a full chapter explaining what branches are and how to use them With the first two chapters of Part II out of the way you ll be ready to start exploring the history of changes you ve been creating Chapter 6 Working with Git s History on page 80 covers that
180. s and 43 44 changing 37 39 cloning 48 118 committing to 55 58 creating 37 exporting 124 125 file management 61 64 file status and history 58 61 Gitosis and 152 154 history compacting 123 124 hosting services for 171 172 log messages for 42 milestones marking 110 112 private 95 public 154 155 release branches 112 114 releases and 45f 46f 44 47 shrinking 143 tracking 115 116 tracking changes in 40 41 129f 128 130 tracking submodules for 116 121 see also History repository Remote repositories Resources bundles 167 online 13 172 173 repository hosting 171 172 third party tools 168 171 Reverting commits 93 Revision control system RCS 146 Revisions 18 82 Server setup see Gitosis SHA secure hash algorithm 39 Squashing 70 96 SSH 101 SSH public key 149 152 ssh keygen 149 150 Staged changes 52 Staging area 52 Status check 59 Straight merging 69 Submodules 116 121 Subversion 11 58 commands for 165 commands in Git 137f Git communication and 139f 136 139 importing to Git 141 144 keep up to date with 143 145 pushing changes to 145 SVN Core pm missing file 140 Syntax names 114 a RE Tags 20 21 44 84 110 112 114 115 Tcl Tk GUI toolkit 33 TextMate Git Bundle 169 TicGit 170 Torvalds Linus 10 Tracking projects 115 116 Tracking tags 20 21 Trunk 43 U Upstream repository 19 URL components 101 102f Username 32
181. s and make sure they have yours Each developer still sends their changes back to the main project repository They can have access to send the changes directly to the main repository an action called pushing in Git or they might have to submit patches which are small sets of changes to the project s maintainer and have them update the main repository 1 2 What Should You Store The short answer everything The slightly less short answer everything that you need to work on your project Your repository needs a copy of everything in your project that s essential for you to modify enhance and build new versions of it The first and most obvious thing you should store in the repository is your project s source code Without that you can t fix bugs or imple ment new features Most projects have some sort of build files A couple of common ones are Makefiles Rakefiles or Ant s build xml These need to be stored so you can compile your source code into something usable Other common items to store in your repository are sample configura tion files documentation images that are used in the application and of course unit tests Determining what to include is easy Ask yourself If I didn t have X could I do my work on this project If the answer is no you couldn t then it should be included Like all good rules there is an exception The rule doesn t apply to tools that you should use You should include the Ant build xml
182. s into a rich toolkit Its following strengths can help you as a programmer Distributed architecture Disconnect completely and work without the distractions of an always on Internet connection Easy branching and merging Creating branches is easy cheap and fast and unlike some version control systems merging every thing back together even multiple times is a snap 1 As I write this we re in the middle of a 700 billion bailout of the American banking system so maybe a bank isn t the best of analogies Don t think about that part just think of banks the way they re supposed to work WHO s THIS BOOK FOR Subversion communication Are you the only one in your company ready to make the switch No worries if everyone else is still using Subversion Git can import all your history from and send your changes back to a Subversion repository That s the sixty second introduction to Git and the rest of this book will build on this simple foundation Who s This Book For This book has something in it for everyone If you re new to version control and the preceding paragraphs are all you know about it this book will walk you through the basics and get you up to speed on how Git can help you If you re a seasoned developer and have a firm grasp on Subversion or CVS you can skim Part I about Git specifics and jump into Part II to get into the good stuff the Git commands and how they work What s in Thi
183. s of Git that you need to know to round out your knowledge Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 Chapter 9 Bevond the Basi Git is a rich toolkit So far in this book we ve covered how to use the day to day features of Git the basics That barely scratches the sur face of Git Git currently ships with more than 140 different commands Many you will probably never have to use Commands such as git check ref format which Git uses internally to determine whether a string is a valid branch or tag name is of use only to those creating extensions to Git But there are some commands that you won t use every day that are extremely useful when you do need them This chapter is devoted to those topics which include the following Compacting your repository history Exporting your repository Rebasing a branch s history against its parent Using the reflog to fix your repository Bisecting your repository to find what change introduced a bug This chapter uses the mysite repository you ve been creating throughout the book If you haven t been following along you can create a clone of the work that s been done up to this point by using the following command prompt git clone git github com tswicegood mysite chp8 git Initialized empty Git repository in work mysite chp8 git remote Counting objects 56 done remote Compressing objects 100 49 49 done remote Tota
184. s similar to this you have everything you need and are ready to go There are two possible error messages you might get instead of the previous output Git complains about SVN not being a command or a fatal error An error saying that it can t find SVN Core pm Not a Git Command or Fatal Error This is a common issue when you install Git through a package man ager such as Ubuntu s apt get or OS X s MacPorts They break Git into multiple smaller packages to reduce the number of dependencies when installing packages To install git svn on Linux you need to locate the package that contains the Subversion subcommand for Git In Ubuntu this package is aptly named git svn prompt sudo apt get install git svn If you installed using MacPorts the way we discussed in Section 2 1 Installing Git on page 26 then you already have git svn installed Like wise if you compiled Git from source it s already available Missing SVN Core pm The other error you might receive is Perl complaining about a missing SVN Core pm file This is caused when you don t have the Perl bindings for Subversion installed There are a couple of ways to get the necessary files The easiest way for most people is to use their package manager On Ubuntu the missing package is called subversion perl To install it type the following prompt sudo apt get install subversion perl Report erratum Prepared exclusively for Frode Nilsen 2 0 printing Ma
185. s that are displayed by git commit are normally unique enough that you can use them without having to use the full forty character hash In order to keep lines short I use the shorter form throughout the book but git log always displays the full hash Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 MAKING CHANGES id Joe Asks WhatAre SHA 1 Hashes and Why Does Git Use Them If you re working with a centralized VCS where one server has The authority to designate one number to each commit num bers make sense If you re working in a distributed environment They don t When two different people are working on the same code who s to say what revision 181 is between the two of them Git addresses this by using SHA 1 hashes SHA stands for Secure Hash Algorithm It s an algorithm devel oped by the U S National Security Agency NSA to produce shorter strings or message digests of known data with little pos sibility of a collision with another hash Git generates commit names by using some metadata from The repository your information as the person making the com mit and the current timestamp This data combined produces a unique hash that has a small probability of ever colliding with another commit The possibility does exist though but it s low enough we can safely ignore it For those math majors out there or those who like trying to pronounce large numbers the cha
186. site release HEAD gt mysite release zip The first line contains the format parameter we talked about The sec ond contains the prefix parameter Notice that there s a trailing for ward slash at the end of mysite release Without that git archive adds Report erratum Prepared exclusively for Frode Nilsen REBASING A BRANCH lt 125 the string to the beginning of every filename rather than putting it in a directory The last line has two parts First it specifies the commit you are cre ating the archive from HEAD After that it tells your shell to put the output from git archive into the mysite release zip file by using gt which is a greater than symbol The command to create a tarball or tar of your repository is simi lar You have to provide an additional command instead of directing the output of git archive directly to the file You can create a mysite release tar gz file by executing this command prompt git archive format tar N prefix mysite release N HEAD gzip mysite release tar gz Notice that after HEAD you use the pipe to pass the contents to the gzp command which then generates the mysite release tar gz file You can replace gzip with bzip2 to use bzip2 compression instead of gzip Exporting your repository as either a tarball or as a zip file gives you a convenient way to distribute a snapshot of your repository to people who don t need or in some cases don t want the
187. sitory Clone an SVN Repository with Standard Layout at Revision 2321 prompt git svn clone s r 2321 Clone SVN Repository with Standard Layout and Add Prefix to All Remote Branches prompt gt git svn clone s prefix svn lt svn repository gt Update from Upstream SVN Repository and Rebase prompt gt git svn rebase Push Commits Back to Upstream SVN Repository prompt gt git svn dcommit View List of Commits That Would Be Pushed Upstream prompt gt git svn dcommit n View SVN Log of Repository prompt gt git svn log View SVN Blame for a File prompt gt git svn blame lt some file gt Report erratum Prepared exclusively for Frode Nilsen Appendix B her Resources and Tool Git is a growing and maturing open source project This book outlines the core tools you need to work with Git daily but you can access a whole host of other tools and resources as you work to get the most out of Git Extras Bundled with Git Git has many great tools that are packaged directly with it Installing it through a package system such as apt get or MacPorts means you might have to install these tools separately gitk Arguably one of the most useful tools in Git gitk visualizes your reposi tory s history showing you how all the various branches come together in the history gitk is billed as the original Tcl Tk GUI for browsing the history of a Git repository It requires Tcl Tk which is already installed
188. stalled for all users of your computer If you want to install it for yourself you can leave the prefix usr local part out Compiling Git takes a few minutes Once it s completed you can install it by using this prompt sudo make install install doc Once that s completed you can run git version from the command line to verify that Git has installed You should see something like this prompt git version git version 1 6 0 2 3 http git or cz Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 INSTALLING GIT Md 28 Check with your distribution s community and or vendor if you re un comfortable compiling software from source They may be able to point you to a more up to date package Installing on OS X If Mac OS X is more your style and you want to use a package manager MacPorts keeps its copy of Git relatively current To install Git using MacPorts use the ports command from Terminal prompt sudo port install git core svn doc This command installs both Git and git svn which well talk about in Chapter 10 Migrating to Git on page 136 There is also an installer package for Git that is maintained on Google Code This installs Git and also has instructions for adding an Open in Git icon to the Finder If you want to compile from source you need to have Xcode the devel opment toolkit from Apple installed The command for compiling Git is similar to that i
189. sting site repo or cz offers free Git repository hosting to open source projects It is limited to open source only but it houses a large collection of repositories It is based around the Gitweb package so the interface should be famil iar to those who have set up Gitweb for their repositories The URL is http repo or cz GitHub GitHub is familiar to nearly everyone who has viewed a Git repository of an open source project It is the hosting provider used for this book s repositories it hosts the Rails repository and it is home to many of the tools listed in this appendix It offers several unique features In particular it adds a social aspect to software development by allowing people to track who has forked a project Its tracking makes it easy for you to see all the developers who are contributing code to a project Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 ONLINE RESOURCES 4 172 GitHub is free for open source projects but it also offers private hosting for a fee for companies that want to use GitHub to manage their own private projects You can get more information and sign up by visiting its website http github com Gilorious Gitorious is another free Git hosting provider The user interface is sim ilar to GitHub and it offers some similar features with two exceptions There is no hosting of private repositories on Gitorious The source code for Gitorio
190. stributed ticket system within Git TicGit stores all your ticket information in a branch inside your repos itory so whoever clones your repository also has a copy of the tickets associated with it The only interface right now is through the command line but a web interface is planned You can download the latest and get an introduction on how to interact with TicGit on the TicGit website http github com schacon ticgit wikis Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 GIT REPOSITORY HOSTING 4 171 git sh Reading this book you no doubt noticed that git is typed a lot git sh removes the need to type git before every command in Git you can type checkout when you want to check out or commit when you re ready to commit changes It does this by launching a customized shell and creating aliases for all the Git commands It also adds the name of your current repository and the branch you re on to your command prompt so you don t have to type git branch to see your current branch The code and installation instructions are available on its GitHub site http github com rtomayko git sh B 3 Git Repository Hosting There are several repository hosting services if you don t want to run your own Git server These range from services that allow only open source to commercial paid hosting This section covers a few of the most notable services repo or cz The original free Git ho
191. t amend Once you are satisfied with your changes run git rebase continue Running git log 1 shows you that the last commit is the commit you squashed together in the previous section the commit you told it to edit prompt git log 1 commit b02376dbbb76c356d9d44cf65163293db9147d9a Author Travis Swicegood lt development domain51 com gt Date Sat Oct 4 11 06 47 2008 0500 add link to twitter and blog The rebase is paused now waiting for you to edit the repository Now you can break that commit apart by using git reset to undo the last commit and then creating two individual commits prompt git reset HEADA contact html locally modified prompt gt git diff diff git a contact html b contact html index 64135cb c6cffa7 100644 a contact html b contact htm 13 6 13 14 Report erratum Prepared exclusively for Frode Nilser 98 Prepared exclusively for Frode Nilsen REWRITING HISTORY 4 99 lt p gt a href mailto tswicegood gmai 1 com gt Gmai 1 lt a gt lt p gt lt p gt lt a href http twitter com tswicegood gt Twitter lt a gt lt p gt lt p gt lt a href http www travisswicegood com gt Blog lt a gt lt p gt lt body gt lt html gt tte ttet git diff shows all the changes waiting for you to commit Pull that second link out and save the contact html file With just the link to Twitter commit your change prompt gt git com
192. t The command git status shows you how Git sees your working tree which is your current view of the repository Subversion and CVS users will recognize this as their working copy prompt gt git status On branch master Changed but not updated use git add lt file gt to update what will be committed modified index html no changes added to commit use git add and or git commit a This output tells us that Git sees the modification you made but doesn t know what to do with it yet The file is listed as modified but it s under the header Changed but not updated To commit it you need to stage the change Staging a commit prepares it to be committed There are three places in Git where your code can be stored First the one you work with directly when editing files is the working tree Second is the index which Ill refer to as the staging area The staging area is a buffer between your working tree and what is stored in the repository the third and final area in Git You can use the staging area to stage only the changes you want to commit to the repository We ll talk more about it in Section 4 1 Adding Files on page 52 Turn back to git add to stage the changes you just made to index html It is the same command you used in the previous section to add a new Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 STARTING TO WORK WITH A PROJECT file I
193. t git config global user email you Gexample com Configure Username Email for a Specific Repository Note You can set your username and email address on a per repository basis This allows you to use a different name and or email address for different projects prompt gt cd path to repo prompt gt git config user name Your Name prompt gt git config user email you example com Turn Color On in Git s Output prompt gt git config global color ui auto NORMAL USAGE 34159 Initialize a New Repository prompt gt mkdir path to repo prompt gt cd path to repo prompt gt git init Initialized empty Git repository in path to repo git prompt gt create file s for first commit prompt git add prompt git commit m initial import Created initial commit bdebe5c initial import 1 files changed 1 insertions 0 deletions create mode 100644 lt some file gt Clone a Repository prompt git clone repository url Initialize repo git Initialized empty Git repository in work remote repository gt git Add Git to an Existing Directory prompt cd path to existing directory prompt git init Initialized empty Git repository in path to existing directory git prompt git add prompt git commit m initial import of some project Add a New Remote Repository from within the repository directory prompt git remote add remote repository repository url A 2 Normal Usa
194. t assumes you want to compare against the HEAD if you don t give it a second revision Now that you know how the log works and how to show differences between different revisions of the file let s look at the history line by line 6 4 Finding Out Who s to Blame You re looking at a file in your project and one block of code it might be one line or ten looks out of place Or maybe there s a set of nested conditions that you re trying to wrap your head around so you can refactor it to make it more understandable Looking at the log of a file and differences between revisions can be helpful but there s a more useful command when you need information about a particular block of code git blame prefixes every line with the commit name committer and timestamp Here are the first two lines of git blame output on hello htm with my last name shortened so the output fits on the page prompt git blame hello html 7b1558c index html Travis S 2008 09 21 14 20 21 0500 1 html a5dacabd index html Travis S 2008 09 21 20 37 47 0500 2 lt head gt There s a couple of interesting pieces of information here First the first eight characters on each line show the commit hash Notice that Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 FINDING OUT WHO S TO BLAME 4 87 the first line has a before it That signifies that it s the first commit to the repository Next notice th
195. t matches 18f822e You can also use multiple carets 181822e is two revisions prior to 18f822e and so on On Windows you need to add quotation marks around your revision if it as a caret in it 181822e should be 18f822e otherwise Windows can t process your command properly Report erratum Prepared exclusively for Frode Nilsen LOOKING AT DIFFERENCES BETWEEN VERSIONS 4 85 N The tilde and a number operator subtracts N from the commit name Using the last examples 18f822e 1 is the revision prior to 18f822e and 18f822e 2 is two revisions prior to 18f822e You can mix and match these two operators The following three com mands would all grab the same revision prompt gt git log 1 HEADAAA s log entry prompt git log 1 HEAD 2 log entry sot prompt gt git log 1 HEAD 1AA log entry prompt git log 1 HEAD 3 log entry You can also use revisions with carets or tildes in the ranges we talked about earlier So you can do the following prompt git log HEAD 10 HEAD fatal ambiguous argument HEAD 10 HEAD unknown revision or path not in the working tree Use to separate paths from revisions Oops That s what happens when you specify a revision that does not exist You get the unknown revision error Now that we have all the revisions ranges and filters down let s look at viewing differences be tween a file at different points in history 6 3 Looking at Differences Between
196. t still has limita tions First you have only the latest version of the code To look at the history of changes you have to ask the repository for that information That brings up the second problem You have to be able to access the remote repository normally over a network In this age of always on broadband Internet connections we forget that sometimes we don t have access to a network As I ve worked on this book I ve written parts at my home office in coffee shops on cross country plane flights and on the road as a passenger while traveling across country I even did some of the final editing at a rustic cabin in Lake of the Ozarks Missouri That highlights one of the biggest advantages of a DVCS which is the model that Git follows Instead of having one central repository that you and everyone else on your team sends changes to you each have your own repository that has the entire history of the project Making a commit doesn t involve connecting to a remote repository the change is recorded in your local repository Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 WHAT SHOULD YOU STORE Lets go back to our bank vault analogy for a minute A centralized system is like having one bank that every developer on your team uses A distributed system is like each developer having their own personal bank You might be wondering how you can keep in sync with everyone else s change
197. table mysite members travis susannah Recognize the first group from earlier This configuration adds a new group called team and says that the team members can write to the mysite repository then it gives write access to users travis and susannah For each new repository you want to create add a new writable line with that repositorys name Once again commit your changes and push them to your server After pushing the changes you can add content to your new remote repository You can send content to your new remote repository from any local Git repository Your local repository has to have at least one commit so there is something to send though From the working tree of that repository execute the following command to add a remote repository to your configuration prompt git remote add origin gitQexample com mysite git That adds the mysite remote repository to your local repository s config uration as its origin repository Obviously you need to swap out exam ple com with whatever your server s domain name is and mysite git with the name of your repository Now all that s left is to push the contents of your local repository to the remote repository Thats a simple enough command but remember you have to specify the branch you want to push to since it doesn t exist on your remote repository yet prompt git push origin master Initialized empty Git repository in srv example com git repositories mysite git Counting obj
198. te repository and another developer has a different version Explicitly tracking one commit removes those issues Git determines the commit when you create the submodule then it detaches from the repository A submodule is actually a completely cloned repository that is checked out at one particular commit You Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 USING GIT SUBMODULES TO TRACK EXTERNAL REPOSITORIES 4 120 can see this by changing into the hocus directory and looking at the branch list prompt gt cd hocus prompt gt git branch no branch master This repository has only two commits in it so let s change to the first commit instead of the second Just check out the commit before HEAD prompt gt git checkout HEADA Previous HEAD position was 20cc9dd initial commit HEAD is now at 7901f67 initial commit with README Now you have to tell Git that this is the changed version you want to use You can see that Git realizes there s a change by running git submodule without any parameters prompt cd prompt git submodule 7901f67feaadeeef755734a92febbc7214fb7871 hocus 7901f67 The is the note that this commit isn t the one that Git expects git status also shows that the hocus directory has changed prompt gt git status On branch master Changed but not updated use git add lt file gt to update what will be committed
199. the changes in the file Don t worry about trying to remember all these commands right now There s a that dis plays some help explaining what all the options do when you re looking at a hunk For now type n to skip staging that hunk and then press 7 to exit interactive mode Stage this hunk y n a d e n xxx Commands sx 1 status 2 update 3 revert 4 add untracked 5 patch 6 diff 7 quit 8 help What now 7 Bye Like all the most useful features in Git there s a shortcut to going straight to patch mode without launching interactive mode You can add p to git add to start directly in patch mode For example you can run the following to launch patch mode directly on index html prompt git add p diff git a index html b index html index e812d0a ca86894 100644 a index html b index html 6 7 6 7 body lt h1 gt Hello World h1 ul lt li gt lt a hrefz bio html Biography a li 4 lt li gt lt a href about htm1 gt About lt a gt lt 1i gt lt ul gt lt body gt lt html gt Stage this hunk y n a d e This time enter y to select the hunk Now it s staged and ready to com mit which brings us to committing changes 4 2 Committing Changes Committing is a relatively straightforward process that adds your changes to the history of your repository and assigns a commit name to them Report erratum Prepared exclusively for Frode Nilsen is
200. the domain name and username if needed for the remote repository The only difference between the SSH URL shown in Figure 7 1 and the basic file system URL is the addition of git github com That tells Git to attempt to log on to the github com server via SSH with the username git and then clone the repository located at the tswicegood mysite chp6 git path The username the git in the previous example is optional You don t have to specify the username when you use the same username on your local computer as you do on the remote server In a lot of instances you share a user with other members on your team to log into the server and the remote server checks the credentials you provide to make sure you have access to it git Git has its own protocol that has been designed for speed It is the fastest protocol but it might run into issues with strict firewalls since it uses port 9418 a port that doesn t normally have network traffic In Figure 7 2 on the next page you can see what a repository URL over the git protocol looks like git specifies the protocol followed by the server github com followed by the repository name In this example the full path is not specified When you start a Git server you tell it what directory to look in for repositories to serve All that clients have to do is specify the name of the repository they want to access Report erratum Prepared exclusively for Frode Nilsen 2 0 printin
201. tml b index html 7 6 7 7 lt hi gt Hello World h1 ul lt li gt lt a href about htm1 gt About lt a gt lt 1i gt lt li gt lt a href contact htm1 gt Contact lt a gt lt li gt lt ul gt lt body gt lt html gt That shows you the Contact link you added the at the beginning of the line shows that it s an addition but something is missing The About link doesn t show any change Running git diff without any parameters compares the changes in your working tree against the staging area You know that there are changes there though git status shows that something is staged View the differ ences in the staging area and the repository by adding cached to the call prompt gt git diff cached diff git a index html b index html index e812d0a ca86894 100644 a index html b index html 6 7 6 7 body hl1 Hello World h1 ul lt li gt lt a hrefz bio html Biography a li 4 lt li gt lt a href about htm1 gt About lt a gt lt 1i gt lt ul gt lt body gt lt html gt Report erratum Prepared exclusively for Frode Nilsen 4 4 MANAGING FILES 4 6l Now you see that change you made back in Section 4 1 Adding Files on page 52 Notice that there s a in front of the Biography line This shows you that the line is being removed If colors are on Git also marks the deleted content as red and added content is green Th
202. to the branch before you apply your change Report erratum Prepared exclusively for Frode Nilsen BISECTING YOUR REPOSITORY lt 133 You do that with git bisect reset prompt gt git bisect reset Switched to branch master Of course like all interesting things in Git there s more to git bisect than just the simple case When trying to understand the history of your changes having a visualization of the history can be helpful For this you can use git bisect visualize You can use git bisect log to show the history of what commits have been marked as good or bad if text output is more your style It also comes in handy if you find out later that you ve made a mistake in marking a commit as either good or bad To do that save the output of git bisect log to a file and then remove all the output after the point of your mistake Then supply that file as the parameter to git bisect replay lt some file gt to tell Git to replay the history up to that point All of this is great but a lot of manual work is involved Not only does it add to the amount of work you have to do but it also makes it more error prone because of human error An automated test suite helps but git bisect can take it a step further by automating the running of that test suite for you To do this you need to have a script that can be run from the com mand line that exits with a O exit code when the tests pass or a positive number if the tests f
203. tree that have not been committed yet You have to run git checkout HEAD to pull all the latest changes from the repository to your working tree This gives you an oppor tunity to handle any conflicts through the methods we dis cussed in Section 5 4 Handling Conflicts on page 74 The refspec in its simplest form is a tag a branch or a special key word such as HEAD You can use it to specify which branches to push and where you want them to be pushed For example you can use git push origin mybranch master to push the changes from mybranch to the remote master Now that you have the basics of cloning a repository and keeping your local repository in sync with remote repositories lets cover one final topic adding new repositories 7 5 Adding New Remote Repositories You can push or pull from any remote repository that you have read or write permission on Typing the full name of a repository can be cumbersome especially when you re syncing with the same repositories over and over again Your default remote repository is called origin Its an alias to the full name of your repository whatever you cloned Say your team includes a developer named Erin and you constantly pull changes from her repository Report erratum Prepared exclusively for Frode Nilsen this copy is P2 0 printing March 2009 ADDING NEW REMOTE REPOSITORIES Addin Remote R itory Later Starting to work on a project by cloning is great if th
204. ts prompt git branch about alternate contacts master new The m parameter will not overwrite an existing branch so the new branch the second branch name you provide must be unique Git complains like this if you try to rename a branch using an existing name prompt git branch m master contacts fatal A branch named contacts already exists You can override this behavior by changing the m option to the M option The uppercase M tells Git to force an overwrite if the other branch exists Use this with care Report erratum Prepared exclusively for Frode Nilsen RENAMING BRANCHES lt That wraps up our tour of branches We ve covered the mechanics of creating and maintaining branches Understanding how branches fit into Git is fundamental to being efficient with Git So far we ve covered how to use Git moving forward but a key part of any VCS is how we can use it to see where we ve been The next chapter Chapter 6 Working with Git s History on the next page deals with that Report erratum Prepared exclusively for Frode Nilsen 79 Those who cannot remember the past are condemned to repeat it George Santayana Chapter 6 Working with Git s Hi A key aspect of any version control system is its history Every new file you add and every change you add creates one more commit in its history In this chapter you ll learn how to do the following Inspect the history of your reposit
205. ty Tools More tools are being made for Git every day This section highlights a few of the standout tools All of these are currently maintained outside the official Git distribution but many are created by developers who also contribute to Git GitX GitX is a native OS X clone of gitk It performs the same functions except it looks like a native OS X application You can view any branch one at a time or all the branches at once like with gitk Its latest version includes the ability to create commits similar to git gui It is fairly new with the first commit being made in June 2008 but it was already up to its fourth stable release O 4 by early fall of 2008 It is hosted on GitHub where you can download the latest build and get information on building it from source http gitx frim nl Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 THIRD PARTY TOOLS lt 169 Komodo IDE ActiveState announced that it s integrating support for several DVCSs including Git in the 5 0 release of the Komodo IDE Komodo is an integrated development environment geared toward scripting languages and web development It is built on Mozilla 1 9 the same branch of Mozilla that Firefox 3 is written on ActiveState released the first alpha version of Komodo IDE version 5 0 in August 2008 The current plan is to have the stable release out some time in the fall of 2008 You can obtain information about t
206. u did was use a tag name as the second parameter for git branch It created a branch based on the commit the tag referenced Your new branch looks just like the release branch did when you cre ated the tag It has the same history as your release branch did before you deleted it You can check git log to show it prompt git log pretty format h s 4b53779 Add in a description element to the metadata a5dacab add lt head gt and title to index 7b1558c add in hello world HTML Now make your fix Once you have the fix in place create a new tag prompt git tag 1 0 1 Once the bug is fixed and a new tag is created you can delete the branch like you did with the previous release branch You can t delete the branch you are on so make sure to switch back to your master branch prompt git checkout master Switched to branch master prompt git branch D RB 1 0 1 Deleted branch RB 1 0 1 You might have noticed that git branch D was used to delete the release branch Thats because master doesn t think it is related to RB 1 0 1 because of the new commit We re going to leave it the way it is for a little bit longer we l fix it in Section 9 3 Rebasing a Branch on page 125 Release branches help organize your team s workflow as you approach a release They allow you to insulate a release from any new features or bugs by making sure that only code that s necessary bug fixes final tweaks from client feedback and so o
207. us is available under the Affero General Public License which is similar to the GPL with one addition You must release the source code from any service that uses the AGPL http gitorious org B 4 Online Resources A ton of information about Git is available online This section high lights the main stops for information online git or cz The source for all things Git is the main Git website has links to the latest source code user documentation wiki and many of the projects related to Git http git or cz Git Manual The user s manual is the definitive source on how to do everything in Git It lists all the commands and their options Thanks to the commu nity surrounding Git the documentation is becoming stronger every day Every time you run git help some command you re accessing the user manual The entire command manual is available online as well http www kernel org pub software scm git docs Report erratum Prepared exclusively for Frode Nilsen ONLINE RESOURCES 4 173 Git Mailing List Like many open source projects a lot of the interaction amongst the developers and the community happens on the mailing list git vger kernel org You can subscribe to the mailing list by sending an email with sub scribe git in the body of the message to the following address majordomo vger kernel org git IRC channel Git has an active community on IRC git on Freenode There is always some
208. ut b alternate master Switched to a new branch alternate Notice this time I added a third parameter master The extra parameter tells Git to create the branch from the master branch instead of the current branch You can provide the extra branch to git branch as well and it will create the new branch from whatever branch you specify Now that you have these branches you can start making changes that are tracked in that one branch Next up we ll cover how to merge those changes between branches Report erratum Prepared exclusively for Frode Nilsen is P2 0 printing March 2009 MERGING CHANGES BETWEEN BRANCHES lt 69 5 3 Merging Changes Between Branches These branches are great for organizing your repository but you need to be able to share changes between branches This is done through merging Merging does exactly what it sounds like It takes two or sometimes more branches and merges them into one There are a couple of dif ferent ways to merge changes between branches This section covers the following Straight merges take the history of one branch and the history of the other branch and attempt to merge them together Squashed commits take the history of one branch and compress or squash it into one commit on top of another branch Cherry picking a commit pulls a single commit from a different branch and applies it to the current branch Straight Merging A straight merge takes one
209. ut it isn t the only one A remote repository can be configured later if you start working on a project by yourself and then need to share it See the sidebar on page 107 for details Your local copy created by cloning works like it would if you had created it yourself using git init the only difference is that you get the history of the repository up to the point you created the clone You use the git clone command any time you want to clone a repository to work with In its simplest form it takes only one parameter the name of the repository you re cloning I m sure you re familiar with this by now there s been a git clone at the beginning of each chapter in Part II of this book Let s clone one more time and grab the repository that we had from the previous chapter prompt git clone git github com tswicegood mysite chp6 git Initialized empty Git repository in work mysite chp6 git remote Counting objects 37 done remote Compressing objects 100 31 31 done remote Total 37 delta 10 reused O delta 0 Receiving objects 100 37 37 4 08 KiB done Resolving deltas 100 10 10 done Report erratum Prepared exclusively for Frode Nilsen copy is P2 0 printing March 2009 KEEPING UP TO DATE 104 This downloads the repository stored on the server and sets up a local copy of it in the mysite chp directory You can change into that directory and see the contents the five files we created earlie
210. while we explore various ways to view what has changed in your repository 4 3 Seeing What Has Changed Its easy to remember that you added a new file or made a change to one file when it s fresh in your mind Sometimes you don t have that luxury though Someone walks into your office or you get caught up in preparation for an impending deadline right after you stage a change Report erratum Prepared exclusively for Frode Nilsen this copy is P2 0 printing March 2009 SEEING WHAT HAS CHANGED 4 59 You need to find out what has changed in your working tree and how it has changed You can use two of Git s commands git status and git diff to do that Viewing the Current Status You can use git status to see all the changes that have occurred in your repository The output it generates is based on the status of any staged commits and how your current working copy compares to what is tracked by the repository There s still that change you staged earlier You can see it right now with git status prompt gt git status On branch master Changes to be committed use git reset HEAD lt file gt modified index html to unstage Note that it has the header Changes to be committed That tells you that it s waiting to be committed Let s add another change This time add a Contact link after the About link Here s the new line I added lt li gt lt a hrefz contact html Contact a li
211. wo commits The first commit s message is add link to twitter This is the 2nd commit message add link to blog You can combine it to say what you like and then save and exit so Git can finish the rebase operation You can see the new history with another call to git log prompt git log pretty format h s HEAD 4 7509494 copy original to show cross file blame 8184d47 adding copied lines to showcase git blame 9a750b3 commit of original text file b02376d add link to twitter and blog Now lets undo those changes by breaking b02376d back into two commits Report erratum Prepared exclusively for Frode Nilser REWRITING HISTORY lt Breaking One Commit into Multiple Commits You just reordered a commit and squashed two commits into one Breaking one commit into two is a little more involved but it starts out the same way Call git rebase i again Once the editor launches edit its contents to look like this prompt gt git rebase i HEAD 4 launches editor edit b02376d add link to twitter and blog pick 9a750b3 commit of original text file pick 8184d47 adding copied lines to showcase git blame pick 7509494 copy original to show cross file blame Notice that the first line says edit now Save and exit to start the rebase When Git gets to the commit you told it to edit it stops and prints the following Stopped at b02376d add link to twitter and blog You can amend the commit now with git commi
212. xtremely lightweight operation The git init command sets up a directory called git that stores all the repository metadata and the empty directory we re in mysite serves as the working tree of code you have checked out from the repository 3 2 Making Changes Now that we have an empty repository it s time to add a file to it Create a file called index html and add a header with the text Hello World in it It should look something like this html body lt hl gt Hello World hl body lt html gt This gives us a basic HTML page to start tracking We ll add some more to it as we continue Now that we have this file it s time to tell Git we want to track it This is a two step process First we have to tell Git to add the file to its index using the command git add then we create a commit using git commit prompt git add index html Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 MAKING CHANGES prompt gt git commit m add in hello world HTML Created initial commit 7b1558c add in hello world HTML 1 files changed 5 insertions 0 deletions create mode 100644 index html git add takes a file or the list of files you want to track as its parameter Git has a couple of other useful ways to add files that we ll talk about in Section 4 1 Adding Files on page 52 git commit creates a commit Commits are the individual pieces of history stored by the repositor
213. y Each one marks the progression of your code Git stores your name and email address from the configuration we did earlier and adds a message to each commit That s what the m and string in the earlier command are for The com mit message is add in hello world HTML Properly written log messages are the killer feature of any version control system They re a place to explain the reason of your commit What does the new file do Why did you change the code For more information writing good commit messages check out the Joe Asks on page 42 So far you ve added a new file to the repository You can see your com mit by running git log commit 7b1558c92a7f7554d834335245051384d98f104e4 Author Travis Swicegood development domain51 com Date Sun Sep 21 14 20 21 2008 0500 add in hello world HTML The first line here shows the commit name Commit names are SHA 1 hashes generated by Git to keep track of a commit Git uses these hashes to make sure that each commit identifier is completely unique something that s important in a distributed environment For more on why check out the Joe Asks on the following page You might have noticed that the commit name displayed in the git log output starts with the same seven characters as part of the output from git commit That s because git commit shows you an abbreviated form of the commit name the full forty character SHA 1 hash would take up too much space The seven character
214. you got an introduction to tags branches and the art of merging That gives you a basic understanding of how Git works and what a DVCS is Up next we ll dive into installing and configuring Git Report erratum Prepared exclusively for Frode Nilsen 2 1 Chapter 2 Ini j e Before you can use Git you have to install it and do some minimal configuration Installation is a relatively straightforward process In this chapter we ll do the following nstall Git Get it configured ntroduce you to Git s GUIs Show you how to use Git s built in help Once we re finished you ll be ready to start using Git to manage your projects Installing Git If you feel comfortable with Makefiles and make is your constant com panion when adding new software to your computer you can skim most of this section If you ve never heard of any of these don t worry this section walks you through the process of installing Git for the first time Git has its heritage in the Linux world It was originally meant to be downloaded as source code and compiled Most modern distributions of Linux have a version of Git in their package repositories and both Fink and MacPorts have Git packages If you re on Windows you have several options to get Git up and running which you ll learn about in Section 2 1 Installing on Windows on page 28 m p www finkproject org p www macports org INSTALLING GIT I
215. you have a change on your master branch that is not included on your release branch Let s switch to the release branch and make the final change to it before it s ready for release The command to switch is git checkout prompt git checkout RB 1 0 Switched to branch RB 1 0 If you had your index html file open your editor is probably complaining about the file changing Go ahead and reload the file Now your changes from the master branch have been removed they re still safely stored in the other branch The final change that needs to be added to your file before it can be released is a description metatag Add a description so the code in your head block looks something like this head lt title gt Hello World in Git lt title gt meta name description content hello world in Git gt head Save and commit your changes prompt git commit a editor launch create log message save and exit Created commit 4b53779 Add in a description element to the metadata 1 files changed 1 insertions 0 deletions Now it s ready to release Now it s time to mark the release with a tag 3 5 Handling Releases Your code is ready for its 1 0 release It s time to tag it Tagging code in Git marks a specific point in the history of the repository so you can refer to it easily Since this is the 1 0 release tag it with that number prompt git tag 1 0 RB 1 0 The two parameters specify the name of the tag
216. your changes You can copy all the code into another directory and start making changes but then there s no way to track the changes you make and more importantly undo the bad changes you make while experimenting This is where branches come in You can create a branch that marks a point where the files in the repository diverged Each branch keeps track of the changes made to its content separately from other branches so you can create alternate histories l http en wikipedia org wiki Choose Your Own Adventure Report erratum Prepared exclusively for Frode Nilsen 2 0 printing March 2009 Create Branch release branch M M N N master branch some other branch Figure 1 1 How branches work You can see how branches work in Figure 1 1 Your master branch is the main line of development Some other VCSs call this their trunk Your branches then branch off that line The branch can exist for the rest of the project or for just a few hours It can be merged into another branch but there s no hard rule saying a branch has to be merged Sometimes you don t even want them to merge It might be a branch to track an older major version of your project or it could be an experi mental branch that may end up getting deleted Just like everything in Git branches can be created locally without having to share them Creating local branches and not sharing them does have its benefits You can experiment w
217. ystem You can quickly find old versions of the software and look through the history of a file to figure out how it got to its current state All this information can be overwhelming though A good strategy for organizing your repository is important to making sure you can find your way around all the history you create This chapter explains how to do the following Mark milestones within your project with tags Handle release branches to focus development when you re about to make a release Group your tags and branches in directory like structures Track multiple projects using one or multiple repositories Use Git s submodules feature to track external repositories This chapter uses the repository you ve been working with If you don t have the repository you can clone the latest from GitHub prompt git clone git github com tswicegood mysite chp7 git Initialized empty Git repository in work mysite chp7 git remote Counting objects 53 done remote Compressing objects 100 47 47 done remote Total 53 delta 19 reused O delta 0 Receiving objects 100 53 53 5 72 KiB done Resolving deltas 100 19 19 done MARKING MILESTONES WITH TAGS 34110 8 1 Marking Milestones with Tags As your repository progresses it is going to have milestones it will be deployed new versions will be created and so on Tags give you a convenient way to mark such milestones so you can come back to them later T

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