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Pragmatic Guide to Git

1. Stage an entire file to commit prompt git add path to file accu aua prompt git add path or everything under the current directory prompt git add prompt Add all files in the current repository prompt git add A all prompt Add all tracked files that have been changed prompt git add u update prompt Choose which changes to commit prompt git add p patch specific file prompt git add p path to file prompt Open the current diff in the editor prompt git add e or a specific file prompt git add e path to file prompt Related Tasks Task 5 Seeing What Has Changed on page 32 Task 7 Committing Changes on the next page this copy is P1 0 pri COMMITTING CHANGES Committing Changes Git tracks changes to your repository through commits which you make with the git commit command It is the workhorse of Git and something you ll use a ton Prior to most commits you need to stage the files you want to commit using the git add You can use it to stage specific changes portions of files and other things that are covered in more detail in Task 6 Staging Changes to Commit on page 34 Each commit requires a commit message You can use m and a string in quotation marks as your message or use Git s editor to write a message There s more information on the editor in Task 2 Configuring Git on page 22 You ca
2. Related Tasks Task 30 Viewing the Log on page 98 Task 32 Comparing Differences on page 102 ort erratum load from Wow T r F 5 E TE ST load from Wow eBook AME this copy is P1 0 printing r 2010 ASSIGNING BLAME lt Assigning Blame Despite its combative name git blame is a useful tool for determining what the original developer was thinking Most bugs manifest themselves with an error at a specific point You can use git blame to find out when the problem line was introduced into the repository and use that as a jumping off point for further investigation git blame displays all or a portion of a file with annotations showing when the change was made by who and more importantly in what revision the change was made Armed with that you can inspect the log to determine what the original author intended git blame outputs the following information Short commit ID Author s name Date and time of commit Line number By default the entire file is displayed You can limit the portion of the file displayed by using the L parameter It requires one parameter a number or POSIX regular expression You can specify the point to stop as well by providing a second value as part ofa comma separated string Make sure there s no space between the start the comma and the second value The second value can be another line number a regular expression or a number with a plus or minus before it
3. Performing tasks such as reorganizing files changing file formats and so on requires that files and sometimes entire directories get moved git mv handles this for you You provide it with two options the name of the original file and the new name This works on files directories or symlinks anything Git can track You can move files directories and symlinks into other directories as well Provide git mv a directory as the second option and you re set Git stages the change for you after you call git mv You must call git commit after git mv to make the move permanent git mv won t overwrite an existing file it displays an error instead You can override this behavior by providing force or f Be careful though because this makes Git overwrite the existing file That s dangerous if the existing file you re overwriting isn t tracked by Git You have no way of getting that file back Download from Wow eBook iowebook com this copy is P1 0 printin MOVING FILES IN GIT Move file or directory For example to move README md to README rst use this prompt git mv README md README rst prompt git commit m Changed README from Markdown to ReSTructured text master 810486 Changed README from Markdown to ReSTructured text 1 files changed 0 insertions 0 deletions rename README md gt README rst 100 Move a file or directory into another directory prompt git mv README rst doc
4. Pragmatic Guide to Git Travis Swicegood Edited by Susannah Davidson Pfalzer Download from Wow eBook lt www wowebook com gt What Readers Are Saying About Pragmatic Guide to Git I d heard a lot of the hype surrounding Git It wasn t until I read Travis book that I learned why people are so enthusiastic about it Travis does a great job explaining the power of Git in a digestible format gt Ivo Jansch PHP evangelist author and founder Egeniq com Git can be intimidating and frustrating to new users Pragmatic Guide to Git alleviates that pain with a straightforward concise walk through that arms readers with exactly what they need to use Git productively gt Luigi Montanez Software developer Sunlight Labs This book is a must have for anyone using Git or just getting started with Git It has saved me time in finding the best practices for managing my Git repositories and will sit on my bookshelf as the go to resource for anything Git gt John Mertic Senior software engineer SugarCRM With two years of experience with Git I thought I would have known most everything in Pragmatic Guide to Git After reading it cover to cover I learned that s not the case It s a well organized collection of useful Git techniques for all audiences gt Luke Pillow Software engineer pillowfactory org Travis Swicegood The Pragmatic Bookshelf Raleigh North Carolina Dallas Texas Pragmatic ookshelf Man
5. and stick to it You have to explicitly push a branch to get a local branch to show up on a remote repository Likewise you have to explicitly delete remote branches to remove them You can delete remote branches with a special case refspec and git push branch to delete This is the equivalent of pushing an empty branch to the remote repository 16 Semantic Versioning http semver org is a great place to start Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin HANDLING REMOTE TAGS AND BRANCHES Push tag v1 0 to the origin prompt git push origin v1 0 Total 0 delta 0 reused 0 delta 0 To git internal domain51 pvt sample repo git x new tag vio 9 20 Push all tags to the origin prompt git push tags origin Total 0 delta 0 reused 0 delta 0 To git internal domain51 pvt sample repo git x new tag v0 8 gt v0 8 x new tag v0 9 v0 9 Fetch remote tags and update local tags prompt git fetch tags origin remote Counting objects 42 done remote Compressing objects 100 37 37 done remote Total 42 delta 18 reused 0 delta 0 Unpacking objects 100 42 42 done From git internal domain51 pvt sample repo git new tag v0 8 gt v0 8 new tag v0 9 gt oW new tag vl gt xi Delete the remote branch called beta prompt git push origin beta From git internal domain51 pvt sample repo git delet
6. For example to create a repository inside an existing directory called work existing widget use this prompt cd work existing widget prompt git init Initialized empty Git repository in work existing widget git prompt git add prompt git commit m initial commit master root commit 6e477fa initial commit 101 files changed 4083 insertions 0 deletions create mode 100644 AUTHORS and 100 more files Related Tasks Task 4 Creating a Local Copy of an Existing Repository on the next page Task 7 Committing Changes on page 36 Task 12 Sharing Changes on page 46 Task 44 Initializing Bare Repositories on page 130 rt erratum Download from Wow eB w wowebook com gt CREATING A LOCAL COPY OF AN EXISTING REPOSITORY E Creating a Local Copy of an Existing Repository You need to create a clone of a remote repository to start making changes to it The git clone command initializes a new repository on your computer and fetches the entire history all the changes that have been tracked during the life of that repository After it s complete you can start making changes to the files in your local working tree and tracking commits locally Sometimes you don t need the entire history of the repository You don t always need the last ten years of changes the last year s might suffice You can use the depth parameter to limit how many revisions you fetch This is called a shallow repos
7. Handling Conflicts on page 82 Task 26 Temporarily Hiding Changes on page 86 Task 37 Resetting Staged Changes and Commits on page 114 ort erratum book com gt this copy is P1 0 printing 2010 Download from Wow eBook Ne DELETING BRANCHES Deleting Branches Branches can and normally do outlive their usefulness Once you no longer need one you can delete it from your repository Remember branches in Git are pointers to a commit Deleting a branch doesn t delete any commits just the named pointer that refers to that commit One area where Git differs from traditional version control systems is the expense related to creating and deleting branches It s common to leave branches such as a release branch in the repository indefinitely in Subversion Git doesn t require that Since tags and branches both point to a single commit you can tag your release and then delete the release branch You can always create a new branch from the tag later if you need to make a change and then retag the new version and the history will look like the branch had always been there You can delete a branch with git branch d You must provide the branch name you want to delete Git warns you if the branch you are trying to delete has not been merged into the current branch You can override this behavior by using D capital D This tells Git that you want to delete the branch even if it hasn t been merged in Download fr
8. Looking at the differences between two commits that are far apart might generate a lot more noise than you need You can limit the files shown in the diff by providing a path The best practice is to include the path after a which tells Git This is a path not a revision Without that Git can confuse the path you provide with a branch or tag of the same name Download from Wow eBook lt www wowebook com gt asia this copy is P1 0 printin COMPARING DIFFERENCES View the differences between the current working tree and the staging area prompt git diff A View the differences between the staged changes and repository prompt git diff staged A View the differences between the working tree and a commit in the repository prompt git diff HEAD prompt git diff Commit ID View the differences between two commits You can use a commit ID branch name or tag to reference a commit here prompt git diff first second nee GE om prompt gt git diff first second example prompt git diff 423d021 1e85ac3 jee OE prompt git diff 423d021 1e85ac3 Limit the diff output to a specific path prompt git diff path Related Tasks Task 5 Seeing What Has Changed on page 32 Task 30 Viewing the Log on page 98 Task 33 Generating Statistics About Changes on the following page ort erratum load from Wow T r F 5 S load from Wow eBook AM
9. The new code is between that marker and gt gt gt gt gt gt gt followed by the name of branch or commit ID tag and so on you were merging in How you deal with the conflict and determine which version to use is up to you You can choose one version over the other use one and then the other combine the two changes together or completely remove them both Once you ve resolved the conflict call git add to stage the new changes and then git commit to commit it You might not have anything to commit however For example if you use all the changes from your local branch Git doesn t need to create a new commit Nothing has changed You can also abort a conflict at any time before you commit the changes by resetting your working tree to ORIG_HEAD See Task 37 Resetting Staged Changes and Commits on page 114 for more information on git reset Here s an example of how a conflict can happen between two branches Conflict Both commits change the same line of code eport erratum Download from Wow eBook www wowebook com scopy IS er 2010 this copy is P1 0 printin HANDLING CONFLICTS _ See an example merge conflict The basics of the error message are the same but the files are always different For example here s a conflict in a repository for one of my projects prompt git merge added raw Auto merging dolt py CONFLICT content Merge conflict in dolt py Automatic merge
10. The plus sign shows the start plus the number of lines the minus sign adjusts the start to show the number of lines before the start Remember that the plus and minus are zero indexed For example L 10 10 shows lines 10 through 19 not lines 10 through 20 Git can track content that moves around in a file or is copied from one file to another You can use git blame to show content that has moved around by adding the M parameter You can also track changes copied from another file by using the C parameter It checks the changes in the file against other changes in the repository to see whether it was copied from somewhere else Download from Wow eBook www wowebook com S CODVIS aristis this copy is P1 0 printin ASSIGNING BLAME Display file with entire line by line commit information prompt gt git blame some file Start the output of blame at line 10 prompt git blame L 10 some file Limit the output of blame to lines 10 through 20 prompt git blame L 10 20 some file wax GNE oe prompt git blame L 10 411 some file vee QE saw prompt git blame L 20 11 some file Show ten lines of output from blame starting at a POSIX regular expression prompt git blame L def to 5 10 some file Check the history to see the change was moved and display that information prompt git blame M some file Check the history to see whether the change was copied from somewhere else o
11. gzip my project latest tar gz prompt ase s prompt git archive prefix my project latest output my project latest tar amp amp gzip my project latest tar prompt Create a zip of the repository at tag v1 0 2 prompt git archive format zip prefix my project 1 0 2 v1 0 2 my project 1 0 2 zip prompt na E aes prompt git archive prefix my project 1 0 2 v1 0 2 o my project 1 0 2 zip prompt Export one directory prompt git archive format zip prefix my project HEAD some directory my project zip prompt Related Tasks Task 3 Creating a New Repository on page 24 R rt erratum narninad fram Wawl aBank aanw wonahnnk n Download from Wow eBook www wowebook com this copy is P1 0 printing October 2010 DOING SOME GIT HOUSEKEEPING 2748 Doing Some Git Housekeeping One of Git s key advantages is its speed Keeping it fast requires some tuning however The git gc command provides the tuning tool git gc performs several housecleaning tasks First it removes any loose objects in the repository over a certain age All of those commits you remove via git rebase git reset and so on are still tracked by Git they re just orphaned Second it recalculates the deltas Deltas are the differences between two pieces of content in the repository Many times the first pass at creating the delta is not the most efficient Recalcu
12. merge those changes using any of the methods covered in Part III Fetching is covered in more detail in Task 20 Retrieving Remote Changes on page 72 You can also fetch changes and merge them at the same time using git pull It fetches the changes and then merges them into the current branch You can specify the rebase parameter to have Git rebase your local branch on top of the remote changes see Task 16 Rewriting History by Rebasing on page 60 Pulling is covered in more detail in Task 21 Retrieving Remote Changes Part II on page 74 Sending changes back to a remote repository to share is done via the git push command Consider it the inverse of git pull it sends your changes to the remote repository and merges those changes into the remote branch via a fast forward merge which is a merge where both branches share a common ancestor and only the branch being merged in has changes in it Don t worry if parts of this sound like Greek This is a high level overview without diving into the specifics The next two parts are going to fill in all the missing pieces ort erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 SHARING CHANGES 1 Set up the remote repository You clone a repository Or You add a remote to an existing repository 2a Fetch changes from a remote repository prompt git fetch remote name then merge the changes into your w
13. on the following page Task 40 Retrieving Lost Commits on page 120 ort erratum minar iA e eel n ank FX EN Jownload from Wow OK CO this copy is P1 0 printing ber 2010 ERASING COMMITS lt Erasing Commits You can tell Git to erase commits This is contradictory to most version control systems but you can treat any commit you haven t shared with the rest of the world as something that can be adjusted as necessary A word of caution before we get into specifics though Don t delete commits that you ve shared without a very good reason Deleting commits causes the history to be rewritten causing the ripple effect problems like a git rebase If you re shared commits your best bet is git revert see Task 36 Reverting Commits on page 112 You can use git rebase a couple of different ways to handle deletes First you can add the i parameter to go into an interactive rebase Once launched delete the line or lines for the commit you don t want to keep save and exit the editor and you re off Second you can use onto to tell Git to rebase onto the commit you want to get rid of You must specify three parameters first you specify the commit you want to start on the commit before the commit you want to delete second you specify the commit before the one you want to start at again third you specify the final commit you want available Dissecting the command from the opposite page you
14. uncommitted changes 40 114 unstaging 40 114 iti until parameter for filtering log output 100 Untracked files status 32 URLs repository 70 M version control systems history 9 models 12 version determining 12 vi environment variable 22 viewing branches 56 diffs 98 102 remote repositories 72 status 32 82 VISUAL environment variable 22 Wooo workflow example 13 overview 29 working tree comparing to repository 102 defined 24 deleting changes in 116 resetting 82 114 stashing changes 86 Zo zip format 124 Available in paperback and DRM free eBooks our titles are here to help you stay on top of your game The following are in print as of October 2010 be sure to check our website at pragprog com for newer titles Title Advanced Rails Recipes 84 New Ways to Build Stunning Rails Apps Agile Coaching Agile Retrospectives Making Good Teams Great Agile Web Development with Rails Beginning Mac Programming Develop with Objective C and Cocoa Behind Closed Doors Secrets of Great Management Best of Ruby Quiz Cocoa Programming A Quick Start Guide for Developers Core Animation for Mac OS X and the iPhone Creating Compelling Dynamic User Interfaces Core Data Apple s API for Persisting Data on Mac OS X Data Crunching Solve Everyday Problems using Java Python and More Debug It Find Repair and Prevent Bugs in Your Code Deploying Rails Applications A Step
15. work dolt class Dolt return self params template X url lib urlencod return self handle response response data def generate body self if self method POST internal params self params copy if GET in internal params del internal params GET return self params template X urllib ur encode return data if raw else simplejson Loads data def getattr self name if name in self supported methods self method name elif not name endsvith self attribute stack append name return self def get url self url self url template X domain self api url 7 if Llen self params internal_params self params copy if self method status 1 difference 1left 1 right 1 conflict def handle_response self response data raw False def handle response self response raw False data if raw return data return simplejson Loads data generated url self stack collapser self af getattr self if name in self supported methods self method name elif not name endswith self attribute stack append name return self def get url self url self url template X domain self api url generated url self stack collapser self a 1 if Len self params Actions m Set gvimdiff as the default merge tool prompt git config global merge too
16. 104 e Finally we wrap up this part with a section on blame The logs provide us with excellent information on individual changes In Task 34 Assigning Blame on page 106 you learn how inspect information about each line of a file It s excellent for assigning blame er praise on the other members of your team when you find their excellently unique code Now let s jump into the basic display of your repository s history the log Report erratum Wr ard fram all AL 3 Down from Wow om this copy is P1 0 printing WORKING WITH THE REPOSITORY S HISTORY from VIEWING THE LOG SW Viewing the Log Git s bread and butter is tracking changes to files in your project over a period of time You use the log to view that history You can use git log to view the standard log output Git displays the commit ID author date and commit message for each commit in reverse chronological order Git sends the output through less to keep the output from scrolling past on the screen too fast to be seen You can use the oneline parameter to shorten the log display to show the first seven characters of the commit ID and the subject of the log message It increases the number of commits you can view on one screen and with properly written log messages makes scanning easier Viewing the entire history often gives you too much information You can limit the number of commits git log shows by providing it with N changi
17. 275 83 200 264 320 Continued on next page Title Year ISBN Pages Interface Oriented Design 2006 9780976694052 240 iPad Programming A Quick Start Guide for iPhone 2010 9781934356579 248 Developers iPhone SDK Development 2009 9781934356258 576 Land the Tech Job You Love 2009 9781934356265 280 Language Implementation Patterns Create Your Own 2009 9781934356456 350 Domain Specific and General Programming Languages Learn to Program 2009 9781934356364 240 Manage It Your Guide to Modern Pragmatic Project 2007 9780978739249 360 Management Manage Your Project Portfolio Increase Your Capacity 2009 9781934356296 200 and Finish More Projects Mastering Dojo JavaScript and Ajax Tools for Great 2008 9781934356111 568 Web Experiences Metaprogramming Ruby Program Like the Ruby Pros 2010 9781934356470 240 Modular Java Creating Flexible Applications with OSGi 2009 9781934356401 260 and Spring No Fluff Just Stuff 2006 Anthology 2006 9780977616664 240 No Fluff Just Stuff 2007 Anthology 2007 9780978739287 320 Pomodoro Technique Illustrated The Easy Way to Do 2009 9781934356500 144 More in Less Time Practical Programming An Introduction to Computer 2009 9781934356272 350 Science Using Python Practices of an Agile Developer 2006 9780974514086 208 Pragmatic Guide to Git 2010 9781934356722 168 Pragmatic Project Automation How to Build Deploy 2004 9780974514031 176 and Monitor Java Applications Pragmatic Thinking and Learning Refactor
18. Commits on page 114 e Sometimes you don t need to fix a commit you need to re move it entirely You learn how to do that in Task 38 Erasing Commits on page 116 Fixing and removing commits is the easy part Most issues are bugs in your code Git provides an excellent tool for isolat ing the commit or commits that introduced a bug You learn about it in Task 39 Finding Bugs with bisect on page 118 Finally all of this rewriting can cause issues if you re not care ful One of Git s mandates is to not lose code though so it provides the reflog to help you recover You learn how to nav igate it in Task 40 Retrieving Lost Commits on page 120 Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 FIXING COMMITS 110 Fixing Commits One of the advantages of Git is the ability to fix commits Fixing changes can be as simple as fixing typos that got committed fixing a bug you didn t catch because you hadn t run your unit tests yet or doing something as complex as rearranging an entire series of commits so they are ordered more logically git commit amend is the way to fix the most recent commit It comes in handy for those simple fixes that you catch right away It is a convenience wrapper around using git reset soft HEAD see Task 37 Resetting Staged Changes and Commits on page 114 and git commit c ORIG HEAD You can use the C parame
19. DIFFERENCES Comparing Differences Git s log provides you with the information about a change who made it what their intent was and so on but sometimes looking at the changes made to the code provides more information git diff shows you the changes that were made between two commits You can use git diff to view the changes teferred to as diffs or patches of two different commits or states Most of the time it s called as git diff with no parameters That s the same as telling Git Show me the changes between my working tree and the staging area git diff considers changes that are staged and ready to be committed as part of the repository You can tell Git to show the differences between what is staged and what is stored in the repository by adding the staged parameter Note that this output does not show any changes that are in your working tree but not yet staged You can also provide a single explicit commit ID to git diff to tell Git to compare your current working tree against what is in the repository at that point For example if you want to compare your working tree against the latest commit regardless of what has been staged you can provide the HEAD parameter to tell Git to compare against that commit Most of the time you use git diff one of the ways discussed but you can use it in other ways For example you can provide a first and second commit to compare the differences between those two commits
20. GitHub 13 130 gitignore file 38 gitk 56 Gitorious 130 Gitosis 130 GitX 56 global excludesfile 38 global parameter configuration 22 grep parameter for filtering log output 100 GUI installation 20 GUI tool for merge conflicts 84 gzip 124 H hard parameter rebasing with 116 resetting with 114 hiding changes see stashing history see repository history Homebrew installation 20 housekeeping 126 hybrid repository model 16 I i parameter filtering log output with 100 launching interactive rebase with 116 ignoring case in log output 100 ignoring files 38 INDEX P PARAMETER index resetting 114 staging commits 34 initializing bare repositories 130 repositories 24 installing Git 20 interactive rebasing 90 110 116 L L parameter limiting blame command with 106 listing stashes 86 tags 64 log 95 filtering 100 merges 58 reusing messages 36 statistics 104 viewing 98 log commit option merging with 58 loose objects removing 126 M M parameter limiting blame command with 106 M parameter in commit messages 36 merging with 58 MacPorts installation 20 merge strategies 50 see also merging merge tools 84 merged parameter viewing branches with 56 merging branches 50 56 commits between branches 58 conflicts 60 82 84 fast forward 50 logging 58 in overview of sharing process 46 rebasing 50 60 90 recursive 50 76 status of b
21. The commit the point in the repository that recorded the change is still stored in your repository but it s orphaned You can use the reflog to find that commit even though the normal Git log doesn t show it The Git reflog tracks every time the tip of a branch changes The tip is the commit that a particular branch points to Back in Part IIL Organizing Your Repository with Branches and Tags we talked more about branches and how they are pointers to commits Each time you commit a change to a branch the branch is updated to point to that new commit and the change is logged in the reflog During normal Git usage you don t need to concern yourself with the reflog It s handy for fixing mistakes however For example you run an interactive rebase discussed in more detail in Task 28 Controlling How You Replay Commits on page 90 and a few days later realize that you accidentally removed the wrong commit during the rebase Catching it right after the fact means you can use git reset ORIG_HEAD but since you didn t your options are limited to one using the reflog Running git reflog you can find the commit before you ran your rebase and check it out directly From there you can determine the commit IDs for the missing commit switch to your current branch and cherry pick the change back into your current branch Also available are the subcommands delete and expire which delete specific reflog entries and expire entries
22. Understanding the differences between the two is important to understanding how Git handles remote repositories Remember remotes are read only branches You fetch changes from a remote repository into those branches which are stored locally instead of committing directly to them and then merge those changes as necessary You can use git pull to combine fetching and merging into one command git pull follows Git s convention and assumes that you want to pull from the origin remote repository if you do not specify a remote You must specify a remote if you want to provide a specific branch to pull from You can provide a full refspec two branches separated by a colon to control which branch you are pulling from and which branch you want those changes to end up in You specify the remote branch before the colon and the local branch after the colon You can pull into branches that don t exist You can use the rebase option to tell Git to rebase your local changes on top of the remote changes instead of performing a merge This is the equivalent of running git fetch followed by git rebase This allows you to cleanly apply all your local changes on top of the remote changes that have already been shared Download from Wow eBook www wowebook com RETRIEVING REMOTE CHANGES PART II Pull changes from a remote repository prompt git pull name branch name example is prompt git pull tswicegood master From git
23. Wow com gt this copy is P1 0 printing r2 VIEWING BRANCHES Viewing Branches You need to be able to see what branches your repository has in it so you can switch between them You can use a visualization tool such as gitk or GitX You can use git branch to get the same information however You can view local remote or all branches depending on which parameters you pass to git branch Calling git branch by itself shows you your local branches You can add either the r parameter or the parameter to view only the remote branches or all the branches respectively Your current branch always has an asterisk before it in the output from git branch It s colored green if you turned on color output see Task 2 Configuring Git on page 22 Likewise remote branches are colored red if colors are on One gotcha with remote branches is that the output from git branch a shows their name with a remote prefix git branch r doesn t You can use either name with commands that require a branch name It s useful to see what branches have or have not been merged into the current branch You can see that by using the merged and no merged parameters It s also useful to be able to find out which branches contain a particular commit For example you can track which branches contain a commit that has a known bug in it by using the contains parameter 13 Gitk is a cross platform application written in tcl tk that ships
24. a minute Several commands don t generate any output after they run successfully though For these commands I include an empty prompt after the success ful command to show that there is no output The first reference to each new term includes an explanation of what the term means If you read the book from start to finish you ll know all of the terms from previous introductions to them Did you forget a term or are you using the book as a reference and not reading it straight through You re covered there too You can refer to Appendix A on page 132 there you ll get explanations of all the common and some not so common jargon you ll encounter in this book and in your adventures in Git port erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 How IS DIFFERENT What Version of Git to Use I used the 1 7 x version of Git while writing the majority of this book All of the commands as of this writing work with 1 7 2 1 and should work with the majority of Git 1 6 x versions The installation methods mentioned in Task 1 Installing Git on page 20 all have recent versions of Git available so make sure you re running a recent version and you won t have any trouble following along You can run git version from the command line to see what version you have Before we dive into the tasks let s talk a bit about Git and what makes it unique How Git Is Differen
25. add any new files though only files that have already been tracked and have modifications in them You can control which parts of a file you commit using the p parameter Running this you re presented with each section of the file that has changed and you re given the opportunity to add or skip it You can stage the change by pressing y or skip a change with n s lets you break the change into smaller pieces This and a few other options aren t always available You can press inside patch mode to get a list of all the commands and what they do Taking the control a step further you can directly edit the changes that are being staged by using the e parameter This opens the diff in your configured editor we talked about that in Task 2 Configuring Git on page 22 Your editor has the file in a diff format Aadditions are prefixed with and removals are prefixed with One quirk of Git is that it can t track empty directories at least as of version 1 7 2 1 There s a reason for this in the underlying architecture and the way Git tracks data in the repository but that s a bigger topic than this page allows for To track an empty directory you can add an empty dot file a file beginning with a dot An empty gitignore works see Task 8 Ignoring Files on page 38 I use include in git Report erratum Download from Wow eBook www wowebook com this copy is P1 0 printing October 2010 STAGING CHANGES TO COMMIT
26. beyond a certain point respectively Under most normal circumstances you don t need to use either Rewriting history is a powerful part of the Git toolkit The reflog helps keep you from hurting yourself too much eport erratum Download from Wow eBook www wowebook com scopy is aiiis er 2010 this copy is P1 0 printin RETRIEVING LOST COMMITS View the reflog prompt git reflog Retrieve a lost commit First let s lose a few commits prompt mkdir work tmp repo amp amp cd work tmp repo prompt git init Initialized empty Git repository in work tmp repo git add files a b c d to the repository so we have some commits prompt for iinabcd do echo simple i gt gt i amp amp git add i amp amp git commit m simple i done output from Git prompt git rebase i HEAD 2 delete the simple b commit Successfully rebased and updated refs heads master prompt git log oneline 4325c46 simple c 4b2a2ba simple a re run the for loop above to add a few new commits You can see that you ve deleted the simple b commit Now you can save it with git reflog prompt git reflog 7 1416 HEAD 0 commit simple e ooo on so om 4b2a2ba HEAD 3 checkout moving from master to 4b2a2ba e563dcc HEAD 4 commit simple c 2b469ed HEAD 5 commit simple b prompt git cherry pick 2b469ed Finished one cherry pick master fcc3a79 simple b 1 fi
27. can grab commits one at a time using git cherry pick Cherry picking a commit from another takes that single commit and commits it to your local branch It s pretty straightforward and appears extremely useful in a lot of situations but be careful Cherry picked commits have different commit IDs than the original commit they came from because their parent changed remember that a commit ID is based partially on where it exists in the history and changing the parent changes the commit ID A good rule of thumb is to cherry pick commits only when a merge is not an option in other words backporting a bug fix where the backported change is never going to be merged forward You must specify the commit that you want to cherry pick You can do this with either a commit ID a branch name a tag or some relative reference to any of these Keep in mind that using a branch name or tag means that the latest commit that those reference is cherry picked in not the entire history Normally git cherry pick automatically creates a new commit as soon as it is done You can change this behavior with two different options Use edit or e to launch the editor and change the commit message before committing the cherry picked revision This allows you to edit the commit message but not the actual commit You can use no commit or n to tell Git to stop as soon as the change has been merged and staged You can use this to cherry pick several commits and
28. commit that introduced the bug You can skip a commit if there s no way to test it Be careful skipping commits however Skipping too many can make it impossible for Git to know which commit caused the bug After you ve found the commit with the bug and determined how to fix it you need to move back to the original branch where you started git bisect reset takes care of that You can automate the process of marking a commit as good or bad with a script It can be any shell script The script must use its exit status code to mark whether the commit it is testing is good is bad or should be skipped There are three possible exit code status that cause bisect to mark a commit as good as bad or as skipped 0 to mark as good lor greater to mark as bad 125 to skip Git changes your working tree between each test so make sure that the script you give to git bisect run is independent of the repository history Create the simplest possible test and put it outside of your working tree and then use it there so git bisect doesn t accidentally overwrite it eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin ber 2010 FINDING BUGS WITH BISECT Use bisect to narrow down the buggy commit prompt git bisect start prompt git bisect bad prompt git bisect good some commit id mark each commit as good or bad until you have narrowed the list of commits down to the commit wi
29. github com tswicegood bobby tables branch master FETCH HEAD Pull changes from a different branch into your local branch prompt git pull origin remote branch local branch example s prompt git pull origin development team dev Pull changes and rebase instead of merge To fetch from origin and rebase against its main branch use this prompt git pull rebase origin master From git github com origin bobby tables branch master gt FETCH HEAD First rewinding head to replay your work on top of it Applying add meta tags Related Tasks Task 15 Merging Commits Between Branches on page 58 Task 16 Rewriting History by Rebasing on page 60 Task 19 Adding and Removing Remotes on page 70 Task 20 Retrieving Remote Changes on page 72 Task 22 Sending Changes to Remotes on the following page this copy is P1 0 printi SENDING CHANGES TO REMOTES 772 Sending Changes to Remotes You have to publish your repository somewhere that is accessible to other members of your team You send your changes to that repository using the git push command Calling git push without any parameters causes Git to assume you want to push the current local branch to a branch of the same name on the origin repository You can provide both a remote repository and a branch name git push takes both named remote repositories that is those that have been added via git remote add and full URLs
30. gitignore file to the repository For files that you want to ignore in every repository on your computer you can set the core excludesfile configuration value to point to a file that contains your global ignore rules It follows the same format as the gitignore and git info excludes files Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin IGNORING FILES Ignore a specific file and or path called cache Add the following to gitignore cache Ignore all swp files from Vim Add the following to gitignore SWp Set up a global excludes file Your excludesfile can exist anywhere you want on your computer The following example puts it in your home directory in the gitignore file prompt git config global core excludesfile V gitignore I have the following my gitignore since I m on a Mac and use Vim DS Store SWp Report erratum Wr ard fram all AL 3 Down from Wow om this copy is P1 0 printing UNDOING UNCOMMITTED CHANGES Undoing Uncommitted Changes Git s two step process for tracking a commit means you can have files that are staged for commit that you re not ready to commit You use git reset HEAD or git rm cached depending on the circumstance Scenario 1 You staged a change to file and want to unstage it use git reset HEAD This is the most common use You re telling Git Change the index the staging area to the
31. give Git a chance to do that setup You can add this by removing the local branch and re creating it from the remote branch Don t worry as long as you make sure all the changes in your local branch have been pushed to your remote repository and your local and remote branch have the same things in them you aren t going to lose any commits You can remove remote repositories by using the git remote rm command It removes any tracking branch information in addition to removing the remote definition 15 Most commands that require a remote repository take both remote names what you add with git remote add or the repository URL Report erratum Download from Wow eBook www wowebook com this copy is P1 0 printing October 2010 ADDING AND REMOVING REMOTES X Add a new remote repository prompt git remote add name repository URL example prompt git remote add tswicegood V git github com tswicegood bobby tables git propmt gt Remove a remote prompt gt git remote rm lt name gt example prompt gt git remote rm tswicegood Make the master branch a tracking branch Run these commands after you push to your remote repository for the first time if you want to set up your local branch as a tracking branch of the remote As an example here s the workflow in a project of mine prompt gt git checkout origin master Note checking out origin master You are in detached HEAD state and
32. is deleted using git rm but before the staged deletes are committed There are two steps First reset the index prompt git reset HEAD old Unstaged changes after reset M old outdated py Second check out the files from the repository prompt git checkout old Force a file to be removed prompt git rm f outdated py rm outdated py Related Tasks Task 9 Undoing Uncommitted Changes on page 40 Task 10 Moving Files in Git on page 42 sain Wier sy f ATTI T Download from Wow eBook lt wowebot this copy is P1 0 printing SHARING CHANGES IPM Sharing Changes Remember that Git is different from most traditional version control systems committing a change and sharing that change are two distinct tasks Committing changes is covered in detail in Task 7 Committing Changes on page 36 this task gives you a quick cheat sheet for the various tasks you need to perform to collaborate with others For more detail on these steps see Part IV Working with a Team Once you have a local clone see Task 4 Creating a Local Copy of an Existing Repository on page 26 or have set up a remote after initializing your repository see Task 19 Adding and Removing Remotes on page 70 you need to fetch changes from the remote repository to keep your local branches we ll cover what branches are in just a second in Part Working with Branches in sync using git fetch After fetching changes you must
33. latest version of this file Scenario 2 You have a new file that s been staged that you don t want to commit now use git rm cached Normally git rm is used to remove files from your repository but adding the cached option tells Git to leave your working tree alone Another common problem is making changes that you want to undo completely You can use git checkout to do this but be careful git checkout happily removes all untracked changes from a file or directory You can t get those changes back if they were never tracked by Git Download from Wow eBook jowebook com gt this copy is P1 0 printin UNDOING UNCOMMITTED CHANGES Unstage a modified file that s been staged For example to undo changes to cache py use this prompt git reset HEAD cache py Unstaged changes after reset M cache py If you re not familiar with command line programs you might not recognize that It tells Git that all arguments are done and that the rest are files or paths It s useful when files and branch or tag names clash Undo all uncommitted changes to file Warning Doing this deletes files and cannot be undone prompt git checkout cache py Related Tasks Task 36 Reverting Commits on page 112 Task 37 Resetting Staged Changes and Commits on page 114 Report erratum Wr ard fram all AL 3 Down from Wow om this copy is P1 0 printing MOVING FILES IN GIT Moving Files in Git
34. no counterpart inside the traditional version control world Using git rebase you can rewrite the history of a repository in a variety of ways It is one of the most powerful commands in Git which makes it one of the most dangerous rebase takes a series of commits normally a branch and replays them on top of another commit normally the last commit in another branch The parent commit changes so all the commit IDs are recalculated This can cause problems for other developers who have your code because the IDs don t match up There s a simple rule of thumb with git rebase use it as much as you want on local commits Once you ve shared changes with another developer the headache is generally not worth the trouble git rebase takes a branch the most common use a tag or a commit ID to rebase on top of You can also pass the rebase option to git pull causing it to perform a rebase instead of merging the upstream changes into your local branch git rebase requires a clean working tree that is a working tree with no modified files If you have changes that you re not ready to commit you can stash them see Task 26 Temporarily Hiding Changes on page 86 until you re done A conflict might arise during the replaying of commits Like a conflict during a regular merge a conflict happens when two commits modify the same line of code git rebase stops when this happens and asks you to fix the conflict see Task 24 Handling Conflict
35. platforms and how you interact with a tool is slightly different for each one you use for merging Generally the local copy the original that was in your branch before the merge is displayed on the left with the remote new code on the right Common to all GUI merge tools is the ability to step through each change and choose which version you like You must save those changes before exiting git mergetool looks at the result and stages that as the correct version of the conflicting code You have to commit your changes once the conflict has been resolved just like manually merging the conflicts see Task 24 Handling Conflicts on page 82 git mergetool stages the changes for you that s the only difference Download from Wow eBook vw wowebook com gt this copy is P1 0 printin HANDLING CONFLICTS WITH A GUI Launch a merge tool to handle a conflict prompt git mergetool merge tool candidates opendiff kdiff3 tkdiff xxdiff meld tortoisemerge gvimdiff diffuse ecmerge p4merge araxis emerge vimdiff Merging the files dolt py Normal merge conflict for local modified remote modified doltspy Hit return to start merge resolution tool opendiff class Dolt E return self handle response response data def generate body self if self method POST internal params self params copy if GET in internal params del internal params dolt py REMOTE 45458 py
36. re telling Git you want to rebase HEAD HEAD through HEAD or the last commit onto c2d2245 You can also use git reset to remove any number of the latest commits off the end of your repository You can use hard to remove the changes from both your index and your working tree but be careful This deletes any changes you have in your working tree git stash see Task 26 Temporarily Hiding Changes on page 86 is a good idea if you have changes you want to hang on to Remember you can always use git reflog see Task 40 Retrieving Lost Commits on page 120 if one of these commands goes awry Be mindful of your working tree though It warrants repeating git reset hard deletes uncommitted changes from your working tree and those uncommitted changes can t be retrieved eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin ber 2010 ERASING COMMITS Erase with an interactive rebase prompt git rebase i commit to gt For example to erase commit C2d2245 use this prompt git rebase i c2d2245 launches editor Delete the line that contains the C2d2245 commit and then save and exit the editor so git rebase can run Erase with git rebase onto For example imagine these commits in your repository c2d2245 2245d2c 9 0 9 36 N X ES HEAD 224cd25 Use the following to delete commits 224cd25 and 2245d2c prompt git rebas
37. repositories 26 Subversion repositories 128 color settings 22 color ui setting 22 commit ID calculation of 13 22 cherry picked commits 88 rebasing effects on 60 COMMIT MESSAGES F PARAMETER shortening log display 98 commit messages see messages commits cherry picking 88 comparing to repository 102 deleting 116 editing 34 36 59 110 erasing 116 finding bugs in 29 fixing 110 merging 50 58 rebasing 50 60 90 116 resetting 114 retrieving deleted 120 reverting 112 specifying when viewing branches 56 staging 34 stashing 86 tagging 64 78 testing 118 see also committing changes commit ID committing changes 36 cherry picking 88 to remote branches 69 versus sharing changes 29 staging 34 see also commit ID commits comparing differences 102 compiling documentation 21 compiling Git from source code 20 configuration file storage 22 configuring expiration values 126 Git 22 conflicts handling 82 GUI tool for 84 while rebasing 60 contains parameter viewing branches with 56 Core editor setting 22 core excludesfile 38 creating branches 54 86 repositories 24 tags 64 custom log messages 58 Cygwin installation 20 D dcommit option pushing to Subversion repositories with 128 delete option for reflog 120 deleting branches 62 commits 116 directories 44 files 44 loose objects 126 reflog entries 120 remote repositori
38. status to provide additional functionality Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing ber 2010 CREATING AND SWITCHING BRANCHES Create a new branch from current place in the repository prompt git branch new branch name example i prompt git branch new prompt Create a new branch from another branch tag or commit prompt git branch new branch name starting point example i prompt git branch newer 99a0de8 prompt A Check out a different branch tag and so on prompt git checkout branch example as prompt git checkout newer Switched to branch newer Create a branch and check it out at the same time prompt git checkout b new branch lt starting point gt example prompt git checkout b newest 64648c9 Switched to branch newest A Create a branch with or without tracking Using a remote branch as your starting point implies that track is on Use no track to turn it off prompt git branch track new branch lt starting point gt prompt git branch no track new branch lt starting point gt prompt Related Tasks Task 14 Viewing Branches on the next page Task 15 Merging Commits Between Branches on page 58 Task 16 Rewriting History by Rebasing on page 60 Task 29 Moving Branches on page 92 ort erratum Revel n cr E ad from
39. sync with the repository to which you are pushing prompt git push force rie QUE woes prompt git push f Related Tasks Task 4 Creating a Local Copy of an Existing Repository on page 26 Task 15 Merging Commits Between Branches on page 58 Task 19 Adding and Removing Remotes on page 70 Task 21 Retrieving Remote Changes Part II on page 74 ort erratum book com gt this copy is P1 0 printing r 2010 Download from Wow eBook Ne HANDLING REMOTE TAGS AND BRANCHES Handling Remote Tags and Branches You can push your tags to a remote repository by one of two mechanisms you can call git push and supply the tag name as the reference to push or you can add the tags parameter to git push to push all your tags to the remote Most tags are fetched automatically Fetching changes from master that has several tags in its history causes Git to fetch those tags as well Like git push tags you can explicitly fetch tags via git fetch tags Be careful with tags however Remote tags always win when there are two tags with the same name For example you have a repository that points to v1 0 and your remote repository has a v1 0 that points to a different commit When you pull changes from that remote your v1 0 is going to change to reflect the latest The best way to handle this is through procedure Determine who is responsible on your team for tagging commits and the way you re going to name tags
40. to remote repositories You can provide a branch name to specify which branch to push but in order to provide a branch you must specify a remote repository For example to push your beta branch to your origin repository you would use this git push origin beta You can also use the more verbose refspec syntax if you want to push to a remote branch that is named differently than your local branch The syntax of a refspec for git push is two branches separated by a colon the local branch first followed by the name of the remote branch For example pushing your local master branch to a remote branch named beta you use this git push origin master beta Git attempts to keep you from updating a repository in a way that could cause issues for others who have cloned your repository By default it does not allow you to push non fast forward changes to a remote repository see introduction to Part III Organizing Your Repository with Branches and Tags for more information on types of merges Non fast forward merges are generally caused by one of two things 1 someone else has pushed changes to the remote repository or 2 you ve made a modification to your local repository history For the first case fetch the remote changes and then merge them into your local branch via git rebase or git merge The second case could be caused by a rebase amending commits or resetting the repository You normally don t want to update a remote reposito
41. to separate experimentation from production ready code Git s convention is to treat the master branch as its main line of code You can rename it to anything you want but it s a good idea to keep with the convention You can create a new branch using the git branch command and providing it at least one additional parameter the name of the branch you want to create This uses your current location in the repository as the place to create the branch from You can also create branches starting at points in the history of the repository Provide git branch with the name of the new branch you want to create followed by the commit ID or branch or tag name to create a branch at that point Following the do one thing do it well idiom git branch just creates the branch you have to switch to it You can use the git checkout command to check out the new branch Creating a new branch and checking it out immediately is common in Git You can do both actions with one command git checkout b Like git branch it requires at least one parameter the name of the new branch and takes an optional second parameter specifying the point to create it from Tracking branches store additional metadata information about the relationship between two branches The most common tracking branch is a local branch that tracks a remote branch something Git does for you by default This additional information is used by other commands such as git push and git
42. 4 formats for exporting 124 garbage collection 126 Git compared to traditional VCS 12 history 9 git add command 34 36 git archive command 124 git bisect command 118 git bisect reset command 118 git blame command 106 git branch command 54 56 62 git checkout command 40 54 git checkout HEAD command 114 git cherry pick command 88 git clone command 26 git clone mirror command 130 git commit command 36 110 git config command 22 git daemon 130 git diff command 102 104 git extension 130 git fetch command 46 72 git gc command 126 git info excludes file 38 git init command 24 git log command 98 filtering 100 viewing statistics with 104 git merge command 58 82 git mergetool command 84 git mv command 42 git pull command 46 60 74 git push command 46 74 76 git rebase command 60 deleting commits with 116 interactive 90 110 116 moving branches with 92 git rebase interactive command 110 git reflog command 120 git remote add command 70 git remote rm command 70 git reset command 114 aborting conflicts with 82 undoing rebase with 60 git reset hard command 114 git reset HEAD command 40 git revert command 112 git rm command 40 44 git stash command 86 git status command 32 82 git svn command 128 git svn clone command 128 git sun dcommit command 128 git svn rebase command 128 git tag command 64 git version command 12 GIT EDITOR environment variable 22
43. 76 Removing duplicate objects 100 256 256 done Run a more garbage collection in the most size optimized way prompt git gc aggressive Counting objects 3048 done Delta compression using up to 2 threads Compressing objects 100 2564 2564 done Writing objects 100 3048 3048 done Total 3048 delta 2041 reused 667 delta 476 Removing duplicate objects 100 256 256 done Remove loose objects that are older than a week prompt git gc prune 1 week Counting objects 244 done Delta compression using up to 2 threads Compressing objects 100 228 228 done Writing objects 100 244 244 done Total 244 delta 109 reused 0 delta 0 Related Tasks Task 16 Rewriting History by Rebasing on page 60 anumninadn fre Aie 1 nr AANI Download from Wow IW om gt this copy is P1 0 printing October 2010 SYNCING WITH SUBVERSION Syncing with Subversion One of Git s key advantages over other DVCSs early on was its ability to communicate with Subversion through git svn Though other DVCSs now have integration with Subversion to varying degrees Git still leads the pack git svn is installed by default on most systems but on Ubuntu and other Linux based systems that break up software into individual packages you do need to install it separately see Task 1 nstalling Git on page 20 You can clone a Subversion repository with a standard layout by using g
44. 82 rebase 60 after parameter for filtering log output 100 aggressive parameter housekeeping with 126 all parameter fetching from remotes with 72 amend parameter for fixing commits 36 110 merging with 59 amending commits 36 59 110 see also editing commits apply command 86 apt get tool 20 archive exporting 124 author parameter for filtering log output 100 auto setting for color 22 B backup 124 bare repositories see repositories bare before parameter for filtering log output 100 bisecting 118 blame assigning 106 branches creating 54 86 deleting 62 fetching specific 72 merging 50 metadata 54 moving 92 naming 49 overview 49 53 pulling specific 74 pushing to specific 76 release 49 remote 68 switching 54 topic 49 tracking 54 70 branches parameter cloning Subversion repositories with 128 bugs finding 29 106 118 bzip2 124 p C HEAD parameter reusing log messages with 36 110 C parameter limiting blame command with 106 cached parameter undoing uncommitted changes with 40 case ignoring in log output 100 centralized version control systems 12 Changed but not updated status 32 Changes to be committed status 32 changes committing see committing changes checking out 40 54 114 cherry picking 88 clear parameter stashing with 86 clones shallow see shallow repositories cloning bare repositories 130 remote
45. 90 pop command 86 prefix parameter exporting with 124 prune parameter housekeeping with 126 pulling 46 68 74 pushing 46 76 128 R r parameter deleting directories with 44 viewing branches with 56 rebase parameter in overview of sharing process 46 rebasing 46 60 deleting commits with 116 with git pull 60 with git push 74 interactive 90 110 116 moving branches with 92 Subversion repositories 128 work flow example 50 recursive merges 50 76 reflog 120 regexp ignore case parameter for filtering log output 100 release branch 49 release manager 67 remote branches see branches remote remote repositories see repositories remote remote tags see tags repositories bare 130 comparing to working tree 102 creating 24 exporting 124 housekeeping 126 initializing 24 layouts 15 private versus public 12 24 shallow 26 status of changes 32 Subversion 128 see also repositories remote repository history repositories remote 67 adding 70 cloning 26 128 fetching from 72 models 67 pulling from 74 pushing to 76 removing 70 sharing changes overview 46 tracking branches 70 see also repositories repository history bisecting 118 log 95 98 100 reflog 120 statistics 104 repository URLs 70 resetting commits 114 retrieving deleted commits 120 reverting commits 112 see also erasing commits resetting commits revision numbers 13 reword option in re
46. CING WITH SUBVERSION Create a Git clone of a standard Subversion repository prompt git svn clone s svn example com repo Perform the equivalent of an svn update prompt git svn rebase lt Push changes back to upstream Subversion repository prompt git svn dcommit Or to see what commits would be sent back upstream use this prompt git svn dcommit n Related Tasks Task 16 Rewriting History by Rebasing on page 60 Report erratum Download from Wow this copy is P1 0 printi INITIALIZING BARE REPOSITORIES 0 Initializing Bare Repositories Most Git repositories that you work with have both the repository metadata the files located in the git directory and a working tree the files that you interact with Repositories that are meant to pushed to and pulled from however are generally created as bare repositories repositories that don t have a working tree You use a bare repository to push your changes to You generally need only one but you can have as many as your situation might require For example you might need to create two each one on different servers so a different set of people can access it You need to make sure to remember to push to both repositories though Using these repositories helps you separate the act of committing changes and the act of sharing those changes You keep your local repository private no one can read directly to it and no one can pus
47. CREATING A LOCAL COPY OF AN EXISTING REPOSITORY Clone a repository prompt git clone some repository example prompt git clone git github com tswicegood bobby tables git Cloning into bobby tables remote Counting objects 39 done remote Compressing objects 100 25 25 done remote Total 39 delta 16 reused 26 delta 9 Receiving objects 100 39 39 39 23 KiB done Resolving deltas 100 16 16 done Clone a repository into a specific path prompt git clone some repository some path example prompt git clone git github com tswicegood bobby tables git btbls Cloning into btbls remote Counting objects 39 done remote Compressing objects 100 25 25 done remote Total 39 delta 16 reused 26 delta 9 Receiving objects 100 39 39 39 23 KiB done Resolving deltas 100 16 16 done Create a shallow clone with the last fifty commits prompt git clone depth 50 some repository These are valid Git repository URIs user ssh host path to repo git some domain path to repo http some domain path to repo https some domain path to repo path to repo Related Tasks Task 3 Creating a New Repository on page 24 Task 12 Sharing Changes on page 46 Task 19 Adding and Removing Remotes on page 70 Task 44 Initializing Bare Repositories on page 130 erratum Download from Wow eBook www woweb Part Il Working with Git WORKING WITH GIT Now t
48. E this copy is P1 0 printing r 2010 GENERATING STATISTICS ABOUT CHANGES kl Generating Statistics About Changes The individual commit s changes are important but viewing those changes in aggregate through statistics can provide you with a unique view of the project Git helps you do that through the various statistical outputs it generates Git s git diff stat is the most straightforward of the displays It takes one or two commits remember git diff assumes HEAD as its second commit if you don t specify it and displays stats regarding the changes rather than displaying the diff output It includes file by file changes in addition to the summary statistics Git uses the diffstat command for this so the output may look familiar if you re used to that program Sometimes all you need is the final line of the stats output the number of files changed the number of insertions and the number of deletions Use shortstat to display that information It s the same information displayed at the last line of the main stat output but without the file by file breakdown The output generated by the stat and shortstat parameters is not easily parseable by a computer You can use the numstat parameter to generate a three column output that is easy to parse The first column is the number of inserted lines the second is the number of deleted lines and the final column is the name of the file in question You can generate stat
49. Your 2008 9781934356050 288 Wetware Pragmatic Unit Testing in Cft with NUnit 2007 9780977616671 176 Pragmatic Unit Testing in Java with JUnit 2003 9780974514017 160 Pragmatic Version Control using CVS 2003 9780974514000 176 Pragmatic Version Control Using Git 2008 9781934356159 200 Pragmatic Version Control using Subversion 2006 9780977616657 248 Programming Clojure 2009 9781934356333 304 Programming Cocoa with Ruby Create Compelling Mac 2009 9781934356197 300 Apps Using RubyCocoa Programming Erlang Software for a Concurrent World 2007 9781934356005 536 Programming Groovy Dynamic Productivity for the Java 2008 9781934356098 320 Developer Programming Ruby The Pragmatic Programmers Guide 2004 9780974514055 864 Programming Ruby 1 9 The Pragmatic Programmers 2009 9781934356081 960 Guide Continued on next page Title Year ISBN Pages Programming Scala Tackle Multi Core Complexity on 2009 9781934356319 250 the Java Virtual Machine Prototype and script aculo us You Never Knew 2007 9781934356012 448 JavaScript Could Do This Rails for NET Developers 2008 9781934356203 300 Rails for Java Developers 2007 9780977616695 336 Rails for PHP Developers 2008 9781934356043 432 Rails Recipes 2006 9780977616602 350 Rapid GUI Development with QtRuby 2005 PDF Only 83 Release It Design and Deploy Production Ready 2007 9780978739218 368 Software Scripted GUI Testing with Ruby 2008 9781934356180 192 Seven Languages in Seven Weeks A Pragma
50. and git commit finalizes it You can undo a git rm before you make a commit through a two step process First you have to reset the index using git reset HEAD Be sure to provide the filename if you want to leave other staged files alone Second check out the file from the repository to restore it using git checkout path to file git rm attempts to keep you from accidentally deleting a file that has changes that have not been committed You can override this behavior with f but be careful Forcing Git to delete the file removes the file and all traces of the changes that haven t been committed yet Download from Wow eBook lt www wowebook com gt asia this copy is P1 0 printin DELETING FILES IN GIT Delete a file from Git To delete a file called outdated py use this prompt git rm outdated py rm outdated py prompt git commit m remove outdated py master 42010bf remove outdated py 1 files changed 0 insertions 17 deletions delete mode 100644 outdated py Delete a directory from Git To delete a directory called old use this prompt git rm r old rm old outdated py prompt git commit m remove the old directory master ddbd005 remove the old directory 1 files changed 0 insertions 17 deletions delete mode 100644 old outdated py Get a directory back after deleting it but before committing it This example uses the previous example where old
51. art of the official version they get pushed to the official repository Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 WORKING WITH A TEAM Shard Bob Distributed Alice epository Repositories 7 AN cd N Push Bob You Alice amp Figure 5 Shared and distributed repository layout with three developers Gray circles are the private repositories outlined circles are public repositories In addition to the concept of remotes these tasks introduce two new concepts you use to retrieve and send changes to remote repositories e Fetching or retrieving changes from a remote repository cov ered in Task 20 Retrieving Remote Changes on page 72 e Pushing or sending changes to a remote repository discussed in Task 22 Sending Changes to Remotes on page 76 You might wonder where pulling fits into this The only difference between a pull see Task 21 Retrieving Remote Changes Part Il on page 74 and a fetch see Task 20 Retrieving Remote Changes on page 72 is that pulling merges changes after Git fetches them It s a shorthand way to combine fetching and merging into one com mand All of these changes being retrieved from remote repositories are stored inside your local repository in remofe branches Git treats remote repositories often called just remotes as branches All of the commits from the remotes are stored alongside
52. ase Programming Bill Karwin 300 pages ISBN 978 19343565 5 5 34 95 http pragprog com titles bksqla Debug It Debug It will equip you with the tools techniques and approaches to help you tackle any bug with confidence These secrets of professional debugging illuminate every stage of the bug life cycle from constructing software that makes debugging easy through bug detection reproduction and diagnosis to rolling out your eventual fix Learn better debugging whether you re writing Java or assembly language targeting servers or embedded micro controllers or using agile or traditional approaches Debug It Find Repair and Prevent Bugs in Your Code Paul Butcher 232 pages ISBN 978 1 9343562 8 9 34 95 http pragprog com titles pbdp ET matic Programmers SQL Antipatte Avoiding the Pitfalls of Database Programming o 4 ww BilKarwin r Debug It Find Repair amp Prevent Bugs in Your Code Paul Butcher by Jaque Carter The Samurai Faced with a software project of epic proportions Tired of over committing and under delivering Enter the dojo of the agile samurai where agile expert Jonathan Rasmusson shows you how to kick start execute and deliver your agile projects You ll see how agile software delivery really works and how to help your team get agile fast while having fun along the way The Agile Samurai How Agile Maste
53. aster prompt git merge development Updating af0fe21 290b0d2 Fast forward old README rst 8 1 files changed 2 insertions 6 deletions Merge changes but don t commit prompt git merge no commit development Automatic merge went well stopped before committing Force the creation of a merge commit prompt git merge no ff development Merge made by recursive old README rst 8 1 files changed 2 insertions 6 deletions X Add a one line log message from each merged commit to the merge message prompt git merge log development Specify a custom log message for a merge commit if created prompt git merge m my message development You can use git commit amend to modify the commit message after the fact too Here s an example prompt git merge log no ff development prompt git commit amend c HEAD editor launches Related Tasks Task 13 Creating and Switching Branches on page 54 Task 14 Viewing Branches on page 56 Task 16 Rewriting History by Rebasing on the next page Task 21 Retrieving Remote Changes Part II on page 74 Task 24 Handling Conflicts on page 82 Task 25 Handling Conflicts with a GUI on page 84 ort erratum Jownload from Wow eBook wi 9ok com this copy is P1 0 printing 2010 REWRITING HISTORY BY REBASING Rewriting History by Rebasing Rebasing commits is the one concept in Git that has
54. aster than were in next release better widget is placed on top of those Here s an example g Ndster d d 6 3 o next release o N o better widget o After running git rebase onto use this o better widget o O master o o o N o next release o Related Tasks Task 16 Rewriting History by Rebasing on page 60 Report erratum Download from Wow eBoc vw wowebook com this copy is P1 0 printing October 2010 Part VI Working with the Repository s History WORKING WITH THE REPOSITORY S HISTORY You ve learned all the basics as well as some of the more complex topics in Git It s time to start looking at all that history you ve been building up and put the code in the context it was created in Your repository is a vault of all the changes you and your team have made to your project Git tracks all of those changes and their com mit messages making them viewable and searchable via the log The log is a reverse chronological view of each commit By default it shows you the commit ID the author the committer if that person is different from the author the date and the log message You can show more or less in that output The power of Git s log feature is directly related to how your project handles commit messages The more information you add to your commit message the more valuable the log is to your developers Git convention for commit messages is to break the messages into two
55. ative as well Call git tag without any parameters to list all tags One key difference between tags and branches is that there is no difference between a remote tag and a local tag A tag is a tag ort erratum Download from Wow eBook wowebook com gt this copy is P1 0 printing 2010 TAGGING MILESTONES List all tags prompt git tag v0 1 v0 2 Tag the latest commit as version 1 0 in the current branch prompt git tag v1 0 prompt Create a tag called betal from the next to last commit prompt git tag betal HEAD prompt Related Tasks Task 23 Handling Remote Tags and Branches on page 78 Report erratum ownload from Wow e lt woweb Down from Wow e this copy is P1 0 print Part IV Working with a Team WORKING WITH A TEAM Everything we ve covered up to this point is about working with Git on your own You can use Git like this to track your own projects but that doesn t take full advantage of Git s power You need to be able to collaborate with other developers on your team using Git You share code with other developers using remote repositories Remote repositories are given names to make them easier to re member For example the conventional name for your default re mote repository is origin There are two different ways to share code through a remote reposi tory in Git with a shared repository model or a distributed repository model For a visual o
56. basing 90 Ae SHA 1 hash calculation of commit ID 13 22 shallow clones see shallow repositories shallow repositories 26 shared repository model 14 15 67 sharing changes overview 46 see also fetching merging pulling pushing rebasing shortstat parameter viewing statistics with 104 Signed off by line 88 since parameter for filtering log output 100 skip parameter rebasing with 60 skipping commits 118 conflicts 60 soft parameter resetting with 114 squash option in rebasing 90 staged parameter viewing diffs with 102 staging area see Index staging changes to commit 34 comparing to repository 102 undoing 40 stashing 86 stat parameter viewing statistics with 104 statistics generating 104 status viewing 32 82 Subversion syncing with 128 ee SWITCHING BRANCHES 21 FORMAT switching branches 54 syncing with Subversion 128 EE tags 50 creating 64 and deleting branches 62 tags parameter cloning Subversion repositories with 128 format 124 temporarily hiding changes see stashing testing commits 118 topic branch 49 Torvalds Linus 9 tracking branches 54 70 trunk parameter cloning Subversion repositories with 128 LL u parameter staging files with 34 Ubuntu git svn command 128 installation 20 uncommitted changes deleting 116 undoing 40 114 undoing commits 112 114 deletions 44 rebase 60
57. by Step Guide Design Accessible Web Sites 36 Keys to Creating Content for All Audiences and Platforms Desktop GIS Mapping the Planet with Open Source Tools Domain Driven Design Using Naked Objects Enterprise Integration with Ruby Enterprise Recipes with Ruby and Rails Everyday Scripting with Ruby for Teams Testers and You ExpressionEngine 2 A Quick Start Guide From Java To Ruby Things Every Manager Should Know FXRuby Create Lean and Mean GUIs with Ruby GIS for Web Developers Adding Where to Your Web Applications Google Maps API Adding Where to Your Applications Grails A Quick Start Guide Groovy Recipes Greasing the Wheels of Java Hello Android Introducing Google s Mobile Development Platform Year 2008 2009 2006 2009 2010 2005 2006 2010 2008 2009 2005 2009 2008 2007 2008 2009 2006 2008 2007 2010 2006 2008 2007 2006 2009 2008 2010 ISBN 9780978739225 9781934356432 9780977616640 9781934356166 9781934356517 9780976694021 9780976694076 9781934356302 9781934356104 9781934356326 9780974514079 9781934356289 9780978739201 9781934356029 9781934356067 9781934356449 9780976694069 9781934356234 9780977616619 9781934356524 9780976694090 9781934356074 9780974514093 PDF Only 9781934356463 9780978739294 9781934356562 Pages 464 248 200 792 300 192 304 450 200 256 208 232 280 336 368 375 360 416 320 250 160 240
58. changes from another developer who s working on the same project port erratum Download from Wow eBook www wowebook com this copy is P1 0 printing October 2010 THE GIT WORKFLOW Commit IDs Instead of Revision Numbers Centralized VCS have the benefit of having one system that doles out revi sion numbers Because everyone is committing and sharing their code in one repository that repository can control what numbers it assigns to a particular commit That model doesn t work in a decentralized system Who s to say which com mit is actually the second commit me or you Git uses commit IDs that are SHA 1 hashes instead The hash is based on the code what came before it who made the commit when they made it and a few other pieces of metadata The chances are incredibly small of there being two different commits with the same commit ID Forking Is Good For the longest time forking a project was a bad thing It drained resources away from the main project and merging changes between the two projects was time consuming when possible Git s superior merge capabilities rooted in its distributed nature make merg ing changes from a forked repository trivial In fact the idea of forking is so ingrained in the Git community that one of the largest Git communities online GitHub is built around the concept To offer your changes you fork a repository commit your changes and then ask the original developer to
59. clude in what will be pkg What git status looks like with no changes prompt git status f On branch master nothing to commit working directory clean Related Tasks Task 3 Creating a New Repository on page 24 Task 6 Staging Changes to Commit on the next page Task 7 Committing Changes on page 36 Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing STAGING CHANGES TO COMMIT 2 Staging Changes to Commit Git uses a two step process to get changes into the repository The first step is staging changes through git add Staging a change adds it to the index or staging area This sits between the working tree your view of the repository and the actual repository Through the staging area you can control what is staged from the most coarse grained adding everything within the repository down to editing the changes line by line First you can select individual files or paths to add by calling git add and passing the filename or path as the parameter Git adds everything under a path if you provide that It uses standard shell style wildcards so wildcards work base matches base rb and base py Another quick way to add all files is the A parameter This adds all the files inside the repository that are not explicitly ignored see Task 8 Ignoring Files on page 38 Closely related you can add files that have changed using the u parameter It doesn t
60. consent of the publisher Printed in the United States of America ISBN 10 1 934356 72 7 ISBN 13 978 1 934356 72 2 Printed on acid free paper P1 0 printing October 2010 Version 2010 10 29 Acknowledgments Introduction II Who Is This Book For Howto Read This Book 0 4 55 64440 444 How Git Is Different soe o i ee m ee TRS Git Wo sa uos EES ESA RS Re Online Resouress uos mec eae ae DSS Yd Getting Started Task 1 Installing Git Task 2 Configuring Git Task 3 Creating a New Repository Task 4 Creating a Local Copy of an Existing Repository Working with Git Task 5 Seeing What Has Changed Task 6 Staging Changes to Commit Task 7 Committing Changes Task 8 Ignoring Files Task 9 Undoing Uncommitted Changes Task 10 Moving Files in Git Task 11 Deleting Files in Git 10 12 13 16 17 20 22 24 28 32 34 36 38 40 42 44 Task 12 Sharing Changes CONTENTS Organizing Your Repository with Branches and Tags Task 13 Task 14 Task 15 Task 16 Task 17 Task 18 Creating and Switching Branches Viewing Branches Merging Commits Between Branches Rewriting History by Rebasing Deleting Branches Tagging Milestones IV Working with a Team Task 19 Task 20 Task 21 Task 22 Task 23 Adding and Removing Remotes Retrieving Remote Changes Retrieving Remote Changes Part II Sending Changes to Rem
61. dit commit id example prompt git revert no edit de3245fa Finished one revert launches editor master 3a26b89 Revert simplify this code a bit 1 files changed 1 insertions 1 deletions Revert a commit but don t commit the change prompt git revert no commit commit id Finished one revert wo OF aes prompt git revert n commit id Finished one revert Related Tasks Task 35 Fixing Commits on page 110 Task 37 Resetting Staged Changes and Commits on the following page Task 38 Erasing Commits on page 116 erratum abBank evananar AINA 3 Ani Download from Wow eBook www woweb this copy is P1 0 printing October 2010 RESETTING STAGED CHANGES AND COMMITS SY Resetting Staged Changes and Commits The git reset command lets you change the HEAD the latest commit your working tree points to of your repository It modifies either the staging area or the staging area and working tree Git s ability to craft commits exactly like you want means that you sometimes need to undo changes to the changes you staged with git add You can do that by calling git reset HEAD lt file to change gt This is the most common use of the reset and is like Subversion s svn revert command Remember not to get the two confused For more on git revert see Task 36 Reverting Commits on page 112 You have two options to get rid of changes complet
62. do this at all or do it poorly Git can employ several different merge strategies to merge branches together The first is the fast forward merge Fast forwards are performed when two conditions are met when the branch you are merging in is being merged back into the branch it was created from and when the original branch hasn t had any new commits since the branch was created For an example check out Figure 3 on the next page Fast forward merges do not actually create anything new in the repository They fast forward the branch pointer to the new location Recursive merges are used by default when both the branches have commits that are not in the other branch Git creates a merge commit that has two parent commits the latest commit in each branch see Figure 4 on page 52 Another way to get information from one branch into another is through rebasing the branch Rebasing is a powerful tool in Git that s often misunderstood which is understandable there s no corollary in traditional VCS It s best explained with an example workflow Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 ORGANIZING YOUR REPOSITORY WITH BRANCHES AND TAGS Before a Fast Forward Merge 7 development master After a Fast Forward Merge master 5 development Figure 3 Before and after a fast forward merge Consider the followin
63. e onto c2d2245 HEAD HEAD First rewinding head to replay your work on top of it Applying add API object for interacting with remote API And after the rebase is successful the branch looks like this c2d2245 HEAD Erase the last commit prompt git reset hard HEAD Related Tasks Task 16 Rewriting History by Rebasing on page 60 Task 36 Reverting Commits on page 112 Task 40 Retrieving Lost Commits on page 120 ort erratum eel ey TM r cn TES ad from Wow lt com this copy is P1 0 printing FINDING BUGS WITH BISECT Finding Bugs with bisect Unit tests code review pair programming and any number of practices help limit the number of bugs in your code We all end up having to track down bugs though It s part of software development git bisect helps you limit the time you spend on this unpleasant task by helping you search through your repository s history for the commit that introduced the bug git bisect works by dividing and conquering You know that a particular commit has a bug in it or is bad You also know that a particular point in the past didn t have that bug in it or is good bisect takes the remaining commits divides them in half and sets your working tree to that midway point in the history You can check your repository for the bug and mark it as either good or bad Repeat until you narrow the list of possible commits down to the
64. e latest version is to build it from source The various dependencies can be hard to track down especially if you plan on building the user manual Tools like apt get build dep on Ubuntu are helpful for tracking down all of the dependencies Watch mixing installation tools For example if you use a Mac and have installed most of your software using MacPorts stick with MacPorts if you compile all your own software on Linux now probably isn t the time to start using apt get Switching to Git provides you with enough learning opportunities so be careful to guard that installing Git doesn t cause the yak to get a trim 4 http www macports org 5 http github com mxcl homebrew Homebrew is relatively new tool that handles compiling software on a Mac It stores all of its formulas the instructions for installing software in a Git repository 6 http www cygwin com 7 http code google com p msysgit 8 http code google com p git osx installer 9 http en wiktionary org wiki yak shaving Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing ber 2010 INSTALLING GIT Compile Git from its source code Download the latest tarball from the Git website prompt tar xjf git YOUR VERSION tar bz2 prompt cd git YOUR VERSION prompt make prompt make install You can compile the documentation from source as well Replace the last two lines in the previous s
65. ed beta Related Tasks Task 18 Tagging Milestones on page 64 anumninadn fre Aie 1 nr AANI Download from Wow IW om gt this copy is P1 0 printing October 2010 Part V Branches and Merging Revisited BRANCHES AND MERGING REVISITED Now you have the basics down understand the concepts of branches and have the know how to collaborate with other devel opers It s time to revisit branches and some of the more advanced things you can do with them For basic branch usage see Part Ill Organizing Your Repository with Branches and Tags This part covers tasks related to managing branches once they ve been created For example what happens when you edit the same file in different ways in two branches and then attempt to merge them back together A conflict can occur We cover multiple ways to handle that in this part Coverediin this part e Conflicts are going to happen Git tries to figure out how to handle merging changes as best it can but sometimes it can t Task 24 Hanaling Conflicts on the following page cov ers how to fix cases where a conflict is created e You can also use a GUI tool for managing conflicts Task 25 Handling Conflicts with a GUI on page 84 covers that e Sometimes you need to temporarily hide changes in your working tree We see how you do this in Task 26 Temporarily Hiding Changes on page 86 e There s more than one way to get changes between branches Task 27 Che
66. ed by The Other Travis Finally you can use grep to search through the log messages using a regular expression or regexp It uses basic regular expressions just like the command line tool it takes its name from grep You can tell it to ignore case with the regexp ignore case or the shorter i parameters Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin FILTERING THE LOG OUTPUT Limit the log output to a single file or directory prompt git log some path prompt git log some file View the commits in the last week You can use many kinds of times with since or after Here are a few variations of looking at the last week of commits prompt git log since 1 week won OF ase prompt git log after 7 days sae OFF prompt gt git log since 168 hours View the commits prior to the last week prompt git log before 1 week ia OE aces prompt git log until 7 days ase prompt git log before 168 hours View the log entries by a single committer prompt git log author some user View the log entries containing a regular expression prompt git log grep some Rr eg Ee x dis DE ris prompt gt git log grep some regex regexp ignore case 258 8 WE cae prompt git log grep some regex i Related Tasks Task 30 Viewing the Log on page 98 this copy is P1 0 printi COMPARING
67. efault name for your main remote repository e patch The differences between two states of a file along with metadata explaining which file or files were modified patch mode An interactive mode of staging files via git add or git stash that allows you to stage portions of the change rather than the entire file pull The act of fetching changes from a remote repository and merg ing them into your local branch via git pull This can be done with a standard merge or via a rebase push The act of sending commits to a remote repository Generally used when sending your changes to a repository that others can access rebase Replaying one or more commits on top of another point in the history of the repository Generally used between branches often where the point you are rebasing against is a remote branch recursive merge A merge where a merge commit is created reflog A log of all changes to the point of a branch for example new commits checkouts rebases and so on Useful for fixing bad rebases refspec References to a particular point inside the repository Used to refer to branches it follows the source destination schema Nor mally used with git pull and git push When pulling the source is the remote branch and the destination is the local branch when pushing the source is the local branch and the destination is the remote branch remote Shorthand for remote repository which refers to re
68. ely git checkout HEAD lt file s or path s gt is a quick way to undo changes to your staging area and working tree Be careful with this command however because it removes all changes to your working tree Git doesn t know about those changes since they ve never been committed There s no way to get those changes back once you run this command Another command at your disposal is git reset hard It is equally destructive to your working tree any uncommitted changes or staged changes are lost after running it Running git reset hard HEAD does the same thing as git checkout HEAD with an extra period after HEAD it just doesn t require a file or path to work You can use git reset hard to remove more than staged changes and changes to your working tree You can give it any commit ID to tell Git to reset your HEAD to that and move the current branch to that location For example if you make two commits and then realize neither should be there a quick git reset hard HEAD fixes that You can use soft with git reset It resets the repository to the commit you specify and stages all of those changes Any changes you have already staged are not affected nor are the changes in your working tree Finally you can use mixed to reset the working tree without staging any changes This also unstages any changes that are staged ort erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing tob
69. er you need to add a remote repository to communicate with Let s cover that next Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 ADDING AND REMOVING REMOTES b Adding and Removing Remotes Git allows you to have as many remote repositories as you like It s common to have a different remote for each member of your team in a fully distributed architecture for your repositories Git requires that each remote have a unique name You must tell Git where to access remote repositories You do this using the git remote add command P It requires two parameters a name and a repository URL The first is simply the short name you use to reference the remote repository by The name origin is the conventional name for the repository that you clone from Git uses this convention in several commands that allow you to skip the remote name when you re working with the origin repository The repository URL points to the actual location of the remote repository This can be in another directory on your system or more commonly a repository that is accessible via a network connection Git can transfer over its own git protocol over git using SSH to encrypt the data transfer and handle authentication and over HTTP HTTPS Git sets up tracking branches for you whenever you create a local branch from a remote branch Adding a repository after you start working locally though doesn t
70. er 2010 RESETTING STAGED CHANGES AND COMMITS Reset staged changes but don t erase any changes prompt git reset HEAD Unstaged changes after reset M dolt init py to reset just certain file s prompt git reset HEAD filel file2 and so on Completely undo the last commit Warning Be careful with this command it overwrites the changes in any files in your working tree prompt git checkout HEAD file or path to reset prompt Completely remove the last three commits Remember hard erases any uncommitted changes in your working tree Git doesn t know about those so you can t get them back prompt git reset hard HEAD wee OF ase prompt git reset hard HEAD 3 HEAD is now at 5eada39 add basic read only version of api wrapper Reset last commit and stage the changes This is useful if the commit has a lot changes and only a few files and or paths need to be altered before committing the changes again prompt git reset soft HEAD prompt Undo the last change to HEAD prompt gt git reset ORIG_HEAD Unstaged changes after reset M dolt apis external py if you want to completely remove any changes prompt git reset hard ORIG HEAD HEAD is now at 99a7a58 fix params template Related Tasks Task 16 Rewriting History by Rebasing on page 60 Task 36 Reverting Commits on page 112 Task 35 Fixing Commits on page 110 Task 38 Erasing Commits
71. es 70 stashes 86 uncommitted changes 116 see also resetting commit reverting commits deltas recalculating 126 depth parameter in cloning repositories 26 diffs colorizing 22 statistics 104 viewing 34 98 102 directories deleting 44 exporting 124 moving 42 distributed repository model 15 67 distributed version control systems 12 documentation compiling 21 drop parameter stashing with 86 E e parameter cherry picking with 88 staging files with 34 edit option in rebasing 90 edit parameter cherry picking with 88 editing commits 34 90 110 messages 88 112 EDITOR environment variable 22 editors configuring 22 see also editing empty directories 34 erasing commits 116 see also resetting commits reverting commits errors see bugs finding conflicts handling excludesfile 38 excluding files 38 expiration values 126 expire option for reflog 120 exporting repositories and directories 124 FO f parameter gt FAST FORWARD MERGES IGNORING FILES deleting files with 44 forcing push with 76 overwriting files with 42 fast forward merges 50 fetching 46 72 versus pulling 68 74 filtering log output 100 fixing commits 110 see also editing commits fixup option in rebasing 90 force parameter see f parameter forcing deletion of nonmerged branches 62 deletions 44 overwriting of files 42 recursive merges 76 forking 13 format parameter exporting with 12
72. et feature can be released as a minor version of your software instead of being part of the next major version This is where you can move a branch to make your repository more sane You use git rebase onto to move branches Like a normal git rebase Git replays the commits from one branch against another The difference is that Git takes the branch you re rebasing and instead of replaying it against another branch it moves it to an entirely different one The syntax is more verbose than a simple git rebase that requires only one additional parameter git rebase onto takes three the first is the branch you re rebasing onto the second is the branch you re rebasing from and the third is the branch you want to move ort erratum Download from Wow eBook wowebook com gt this copy is P1 0 printing 2010 MOVING BRANCHES Move branch better widget from next release to master This is the current state of the repository the next release branch was created from the master branch and the better widget branch was created from the next release branch o master o N o next release o N o better widget o The command to move the branch is a specialized version of git rebase prompt git rebase onto master next release better widget After running this command use this o better widget o o master o N o next release o next release is moved to the end of master so if there were more commits in m
73. f these two models see Figure 5 on the follow ing page The one most familiar to those coming from another VCS is the shared repository model A shared repository means that all members of your team can push and pull from the same repository Team members keep their changes locally until they re ready then they push those changes back upstream when they re complete for the rest of the team to use This model is very familiar to anyone used to working with a tradi tional version control system There s very little overhead in deter mining where the code is and what state everything is in You can also use a distributed repository model for handling your repositories Each member of your team has their own private repos itories on their computers plus a public repository that they push their code to Each team member needs to pull changes from the other team members to make sure they have the latest code Most teams using a distributed model designate someone as the release manager It becomes their job to make sure that everything is merged together and that member s public repository becomes the repository of record This is also common in open source projects using Git Many teams see the most benefit from a hybrid of these two ap proaches One repository is considered the repository of record that everyone syncs against and then developers share their changes through their public repositories Once changes are ready to be come p
74. failed fix conflicts and then commit the result You can find the conflict inside the file by looking for the special markup that Git adds followed by a commit most of the time HEAD Here s the conflict in the previous file HEAD def handle response self response data raw False return data if raw else simplejson loads data def handle response self response raw False data if raw return data return simplejson loads data gt gt gt gt gt gt gt added raw Commit a fixed conflict You can use git status to see whether the conflict still exists On branch master Unmerged paths use git add rm file as appropriate to mark resolution both modified dolt py SR RB Once the conflict is resolved call git add and git commit like you normally would Related Tasks Task 15 Merging Commits Between Branches on page 58 Task 25 Handling Conflicts with a GUI on the following page report erratum Download from Wow eBoc vw wowebook com gt this copy is P1 0 printing October 2010 HANDLING CONFLICTS WITH A GUI 7 2 Handling Conflicts with a GUI Merging is often made easier with a GUI that displays each version of the code in question and allows you to choose which version you prefer You can use git mergetool to launch a GUI tool to handle merge conflicts You can choose from several different merge tools Their availability varies between
75. g 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 new titles and other offerings Buy the Book If you liked this eBook perhaps you d like to have a paper copy of the book It s available for purchase at our store pragprog com titles pg git Online Orders www pragprog com catalog Customer Service support pragprog com Non English Versions translations pragprog com Pragmatic Teaching academic pragprog com Author Proposals proposals pragprog com Contact us 1 800 699 PROG 1 919 847 3884
76. g example Rebasing Changes You start your morning by pulling in all the changes from the company s shared repository and then start working During the morning your co worker pushes some commits upstream When you try to push the commits you ve made you get an error You now have two options You can fetch the changes and do the following 1 Merge them into your local branch creating a merge commit 2 Rebase your local branch on top of the remote branch Rebasing takes the commits you made this morning and then replays them one by one starting on the other branch You can do this to keep the appearance of a continuous stream of development instead of having a bunch of merge commits scattered throughout your repository s history Download from Wow N wowebook com gt ORGANIZING YOUR REPOSITORY WITH BRANCHES AND TAGS Before a Recursive Merge 7 master After a Recursive Merge development 7 master Figure 4 Before and after a recursive merge Now let s see what s covered in this part e Before you can use branches you must create them You will learn how to do that in Task 13 Creating and Switching Branches on page 54 Keeping track of your branches requires that you be able to see what branches you have Task 14 Viewing Branches on page 56 covers the commands you need to know in order to see the branches you have in your repository Having multiple branches to separate work on
77. gt You can edit this message to be whatever you want You can use the no edit parameter to tell Git to use the default message without passing it through the editor if the default is sufficient Sometimes you need to revert several commits to completely undo a change You can use no commit or you can use n to tell Git to perform the revert but stop short of committing the change This lets you combine all the revert commits into one commit which is useful if you need to revert a feature that spans several commits Make sure that you revert commits in reverse order the newest commit first Otherwise you might confuse Git by trying to revert code that doesn t exist yet You can use git revert to undo commits that you don t want or need any longer but it does leave a trace In most cases you don t want commits disappearing from your repository For those instances where you don t want a record of your commit at all see Task 38 Erasing Commits on page 116 Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing ber 2010 REVERTING COMMITS Revert a particular commit prompt git revert commit id example prompt git revert de3245fa Finished one revert launches editor master 743d2ef Revert simplify this code a bit 1 files changed 1 insertions 1 deletions Revert a particular commit and use the default message prompt git revert no e
78. h have been amazing as always Without their support and that of the rest of my family and friends this book would not have happened The world of version control systems VCSs has undergone a major shift over the past few years Fast reliable and approachable distributed version control systems DVCSs such as Git have burst onto the scene and changed the landscape of open source software development and corporate software workflows This book is your guide to this new paradigm It s not a complete reference instead it focuses on getting you up and running quickly Pragmatic Guide to Git covers the 95 percent of Git that you ll use at least once a week as well as a few tasks that will come in handy but aren t used as often Git started when the license of VCS software that the Linux kernel used to track changes was revoked After investigating the other alternatives Linus Torvalds decided he could write a better version control system in a few weeks than what currently existed so he set off to do that Git then in a very rough form was the result of that two weeks of hacking together some shell scripts back in the spring of 2005 Linus had to calculate pieces of the commits by hand on the first few commits commits are the changes Git tracks for you Since those original hand rolled commits Git has become the leader in the field of DVCS Who Is This Book For This book is geared for someone new to Git who is looking to get u
79. h called release v1 0 for the 1 0 version to isolate that release from features that aren t supposed to ship until version 1 1 Work on version 1 1 continues like normal in the mas Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 ORGANIZING YOUR REPOSITORY WITH BRANCHES AND TAGS ter branch and any changes from the final work on version 1 0 get merged back into master You can use tags to mark milestones in your project such as re leases Tags are similar to branches except they are read only Once you create a tag you can t change it Well that s almost true but for now consider them completely unchangeable Branches and tags are not shared by default Like commits you re given the ability to decide which branches and tags to share with other developers and when Branches in Git are pointers to a specific commit in your repository s history Since each commit knows about its parent or parents Git can reconstruct what s in a branch by looking at the latest com mit in that branch and walking the history backward to find all the ancestors This simplified approach to branches makes them quick to create rename merge and even delete You occasionally have to merge changes between branches to keep from duplicating the same work in different branches Git makes this easy by tracking which commits have been merged be tween branches for you Many modern VCS do not
80. h to it You use a remote repository as a place to share your changes with everyone else A bare repository works just like a normal repository except it doesn t have a copy of the working tree All of the files that are present in the git of your normal repository are present in the directory where your bare repository lives By convention bare repositories should end in git For example call your bare repository widget git if its name is widget To share your repository place it somewhere that other people can access it This could be a network file system on a directory with proper read permissions on a remote server or even on an HTTP server You can also make it accessible via the git daemon so it is accessible via the git protocol Most third party hosting solutions such as GitHub or Gitorious handle the creation of the bare repository for you You only have to push the changes to the repository they create Likewise if you use Gitosis it handles the creation of a bare repository for you You can use the git clone mirror command if you want to clone an existing repository and populate it with the commits from that remote repository This is useful for creating local copies of a repository to interact with and possibly share without exposing your private local repository 20 http github com 21 http gitorious com 22 http eagain net gitweb p gitosis git eport erratum Download from Wow eBo
81. hanges separately Once I have the feature complete I give the commits I ve created a quick review to make sure all the changes are necessary At this point I look for commits that can be combined and make sure they are in the most logical order Finally once I have those commits ready I share those commits by push ing them push is the term for sending commits to another repository back upstream to my public repository so the rest of the team can view them and integrate them with their repositories Small Teams with a Shared Repository Many small teams use Git like a traditional version control system They have one main repository that all the developers can send changes to and each developer has their own private repository to track their changes in You make your changes locally then when you re ready to share them with other developers you push them back to the repository you all share If someone else has shared their changes since the last time you updated from the shared repository you will get an error You must first get the changes from the shared repository and integrate them into your repository through a process called merging Once the changes are merged you can push your changes to share with the rest of the team Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing THE GIT WORKFLOW Git in Open Source Each open source project has its own methods of accepting changes Some p
82. hat you have Git and your repository set up it s time to start learning how to interact with Git A handful of commands are all you need to get you through most tasks Once you finish the tasks in this part you ll know them all As we saw in the introduction the workflow in Git is different from other version control systems and definitely different from working without any version control system Each time you make a change you want to track you need to commit it The workflow goes like this First create your repository either cre ate a new repository or clone an existing one Then make some changes test that they do what you want commit those changes make some more changes and so on Finally you share those changes when they re ready One thing to keep in mind when working with a distributed version control system like Git is that committing a change and shar ing that change are two different processes This is different from centralized VCS such as Subversion and CVS where the two actions are synonymous This separation provides you with a lot of freedom You can experi ment locally try a whole bunch of things and then share the best solution but to paraphrase an old uncle With great freedom comes great responsibility Lots of small discrete changes that touch very specific portions of The code are better than a few monolithic changes Make sure you don t sit on a whole bunch of changes until they re perfec
83. he last one This command allows you to rewrite history by changing commits In this example say you want to edit the third commit before HEAD prompt git rebase i HEAD 3 launches editor mark the first commit the one you want to change as edit instead of pick then save and exit your editor make the change you want to your commit then prompt git commit amend prompt git rebase continue Related Tasks Task 16 Rewriting History by Rebasing on page 60 Task 28 Controlling How You Replay Commits on page 90 Task 36 Reverting Commits on the next page Task 37 Resetting Staged Changes and Commits on page 114 Task 40 Retrieving Lost Commits on page 120 ort erratum TE TEN reves oa X load from Wow eBook om this copy is P1 0 printing r 2010 REVERTING COMMITS Reverting Commits Sometimes we make mistakes A commit that wasn t supposed to be shared gets pushed to a public repository a commit has a bug that can t be fixed and needs to be undone or maybe you just don t need that code any longer These cases all call for git revert The git revert command does just what you might expect It reverts a single commit by applying a reverse commit to the history You can call git revert with just a commit ID Git launches the editor with the commit message already filled out It follows this pattern Revert some commit message This reverts commit lt some commit hash
84. hen that commit happened and who made it branch A separate line of history within the repository stored as a pointer to a particular commit check out or checkout The act of taking a branch or files from the repository and checking it out into the working tree cherry pick Taking one commit and applying it to the current branch commit The individual points in time that your repository tracks Each commit in Git tracks who made it when it was made the changes that were made and what commit or commits are its direct parents commit ID The ID for each commit is an SHA 1 hash based on the data that makes up a commit Any change to the commit causes a different commit ID to be generated Each commit provides its own integrity check through its ID commit message A plain text message that is stored with the commit It is used to convey what the commit did and why By convention Git GLOSSARY breaks commit messages into two parts The first line is considered the subject followed by an empty line followed by the body ofthe commit message conflict See merge conflict diff Describes the differences between two or more versions of a file or files fast forward merge merge that moves the pointer of a branch to another point in the future without creating a merge commit fetch Retrieving commits from a remote repository and storing them in the local repository HEAD The latest point in your repos
85. it svn clone s and providing Git with the repository URL You can use trunk tags and branches to provide Git with a custom location for your trunk tags and branches Creating a clone is all you need to do if you re migrating to Git from Subversion but Git can continue to talk to Subversion if you re not making the switch There is no direct git svn update available on Subversion clones Instead you use git svn rebase to update your local branch with the upstream changes in Subversion This fetches the changes from Subversion and then rebases your local branch against the upstream changes Remember using rebasing commits whether with git rebase or through git svn rebase comes at a potential cost git svn requires a rebase to keep track of which commits are in Subversion and which are only in Git Because of this it s not a good idea to share changes directly via Git clones of Subversion repositories Use Subversion for sharing changes You can push changes back upstream to a Subversion repository with git svn dcommit You can add the n parameter if you want to see what commits will be sent upstream without actually sending them The output from any of the git svn commands could take up several pages of output so I haven t included any output here 19 http svnbook red bean com en 1 5 svn tour importing html svn tour importing layout Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin SYN
86. ith a working tree but there is another type of repository a bare repo These are used for sharing changes via pushing and pulling to and from They re covered in Task 44 Initializing Bare Repositories on page 130 Now let s start off with exporting your repository Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 EXPORTING YOUR REPOSITORY Exporting Your Repository Sharing your repository with other developers is a matter of giving them access to read your public repository but sometimes you need to give access to content you re tracking to people who don t use Git clients customers or business partners of a less tech savvy variety You can export the contents of your repository at a particular point to share with these people using the git archive command It s important to remember you are exporting only one point in the history of your repository not the entire history Some people look at an export as a backup of their repository This is not the correct way to do a backup in Git Each clone of your repository has the entire history so push your repository to a remote repository on some other computer Backup finished You can specify the point you want to export as either a commit ID HEAD or some other special commit name a branch or a tag You can also specify a relative revision if you want to export the parent of a certain commit Provide a
87. itory There are a few limitations to this type of repository clone For example you can t create another clone from it There is a place for these clones however Say you want to submit a patch a change to a project with a long history You only need the recent changes to show your change against so a shallow repository is perfect Depending on how the firewall on your computer or local area network LAN is configured you might get an error trying to clone a remote repository over the network Git uses SSH by default to transfer changes over the network but it also uses the Git protocol signified by having git at the beginning of the URI on port 9418 Check with your local network administrator to make sure communication on ports 22 the port SSH communicates on and 9418 are open if you have trouble communicating with a remote repository You use git clone to fetch changes when a repository already exists but you don t have to clone a repository to work with a remote repository Remote repositories are repositories that you can talk to generally over a network to push and pull changes from You can initialize a new repository like we talked about in Task 3 Creating a New Repository on page 24 and then add a remote repository later with the git remote command see Task 19 Adding and Removing Remotes on page 70 eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin ber 2010
88. itory that your working tree cur rently points to index See staging area interactive rebase Same as rebase except Git pauses before the rebase is started and allows you to modify the commits that are being applied modify the order in which they are applied and specify which commits should be stopped at so they can be edited log A reverse chronological output of all the commits that by default include the committer commit date commit ID and commit message master Refers to the name of the default branch where the majority of development happens in Git merge Bringing the contents of two separate branches into sync by merging them together This can happen by any number of merge strat egies the most common of which are a fast forward merge and a recur sive merge merge commit commit with multiple parents used to signify a merg ing of two or more branches Merge commits are generally created by recursive merges merge conflict amp conflict that happens when two commits attempt make changes that cannot be reconciled by automated means This generally happens during a merge or while replaying commits during a rebase non fast forward merge See recursive merge ORIG HEAD Refers to the location of HEAD before making any big changes to it such as running git rebase or git reset Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing GLOSSARY origin The d
89. ke to thank a reader of my first book who shot me an email that planted the seed that became this book Next Dave Andy and the entire crew at Pragmatic Bookshelf have been great to work with a second time Both books I ve written for them have been gambles first as a rookie author and then with this book as an author charting the territory of a new format and they haven t blinked an eye My editor Susannah Davidson Pfalzer has been indispensable She was al ways there with advice tips the occasional tough love and an ever optimistic attitude every author should be so lucky Reviewers of early drafts of this book provided me with a tremendous amount of constructive feedback that helped shaped this book into what you re hold ing in your hands or looking at on your computer s screen Thanks to Joel Clermont Javier Collado Geoff Drake Chad Dumler Montplaisir Wayne Huang Michael Hunger Ivo Jansch Jerry Kuch Johnathan Meehan John Mertic Luigi Montanez Karl Pfalzer Luke Pillow Christophe Portneuve Tom Sartain Stefan Turalski Tom Van Herreweghe Matt Warren and Nick Watts No acknowledgments for a book on an open source tool would be complete without acknowledging the work of the legion of volunteers who made the project possible A huge debt is owed by all of us who use Git to the nearly 700 people who have contributed to the project My family and friends in particular my wife whom I m lucky enough to count as bot
90. l gvimdiff Use the Perforce Visual Merge Tool on Windows This example shows the Window specific command but you can use the same process on any platform for a custom merge tool prompt git config global merge tool p4merge prompt git config global mergetool p4merge cmd p4merge exe LOCAL SREMOTE SMERGED Related Tasks Task 15 Merging Commits Between Branches on page 58 Task 24 Handling Conflicts on page 82 17 http www perforce com perforce products merge html Download from Wow this copy is P1 0 printing October 2010 TEMPORARILY HIDING CHANGES Z Temporarily Hiding Changes Some Git operations such as git rebase require a clean working tree a working tree with no changes git stash gives you a tool to hide changes that aren t quite ready to commit so you can come back to them Stashing changes is the equivalent of creating a commit and then resetting your repository back one commit Stash provides a mechanism for grabbing those changes out of history more easily however Stash names are similar to the names you see in the reflog see Task 40 Retrieving Lost Commits on page 120 You refer to them as stash replacing the with the age of the stash The most recent is the one before that is 1 and so on You can call git stash without any parameters to create a new stash Calling it without any parameters is the same as calling it with git s
91. l branches from a remote repository You can change this depending on the parameters you provide to git fetch You can fetch a specific branch by calling git fetch with an explicit remote name and a refspec Refspecs provide the name of the remote branch and the branch in your local repository that it should be fetched into separated by a colon For example to fetch only the master branch from your origin branch you use this git fetch origin master remotes origin master This format might look a little wonky at first glance Most of the time you refer to a remote branch by remote name branch name without the remotes prefix Its full name contains the remote prefix however and you must use its full name with this command You can fetch changes from multiple remotes at one time You can use the multiple parameter to provide Git with multiple remotes to fetch changes from Use all to tell Git to go through all of your remotes and fetch the changes from them Download from Wow eBook lt www wowebook com gt asia this copy is P1 0 printin RETRIEVING REMOTE CHANGES Fetch changes from remote repository prompt git fetch remote name example prompt git fetch tswicegood remote Counting objects 39 done remote Compressing objects 100 25 25 done remote Total 39 delta 16 reused 26 delta 9 Unpacking objects 100 39 39 done From git github com tswicegood bobby tables ne
92. lating the deltas with the help of hindsight allows Git to combine like deltas to reduce the size of the repository and decrease the time Git spends looking for information in the repository Periodic running of git gc helps keep the repository in top shape Providing it with the aggressive parameter tells Git to focus on making the repository as efficient as possible instead of trying to run the command as quickly as possible Git is configured by default to remove loose objects that are older than the gc pruneExpire values The default value is two weeks but you can change this using git config You can also change it by providing a value to git gc via the prune lt some value gt parameter This takes the standard time values Many of the commands that cause the repository history to become unruly automatically call git gc for you The most notable is git svn rebase Older versions of Git required that you run git gc manually to keep the repository size in check It s still a good idea to run git gc from time to time though to make sure your repository is in top shape Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin DOING SOME GIT HOUSEKEEPING Run garbage collection prompt gt git gc Counting objects 3048 done Delta compression using up to 2 threads Compressing objects 100 2564 2564 done Writing objects 100 3048 3048 done Total 3048 delta 2041 reused 667 delta 4
93. les changed 1 insertions 0 deletions create mode 100644 b Related Tasks Task 16 Rewriting History by Rebasing on page 60 Task 27 Cherry Picking Commits on page 88 Task 28 Controlling How You Replay Commits on page 90 Task 42 Doing Some Git Housekeeping on page 126 rt erratum Download from Wow eBook www wowe this copy is P1 0 printing October 2010 Part VIII Moving Beyond the Basics MOVING BEYOND THE BASICS At this point you have learned all of the main topics you need to become a proficient Git user There are a handful of commands that you ll only need to use occasionally Covered in this part e You may need to export the current state of your repository without the entire history You learn how to do that in Task 41 Exporting Your Repository on the following page Git attempts to remain as fast as possible sometimes at the COSt of storage efficiency Task 42 Doing Some Git Housekeep ing on page 126 shows you the commands to run to recal culate your repository s internal structure and save some disk space e Many developers are still working in an environment where Subversion is their company s version control system of choice Git provides bidirectional support for SVN it can both read from and write to an SVN server You learn about that in Task 43 Syncing with Subversion on page 128 Finally we ve talked about repositories exclusively in the con text of repositories w
94. ly in addition to using the git config command You can set every setting on a global or per repository basis By leaving global out of the command the settings will be stored in the repository s git config file You might want to set a few other useful configuration values while configuring Git You can set color ui to auto if you like to have your command line interfaces colorized The auto setting tells Git to use color whenever it is generating output to be displayed but to render plain text whenever the output is being piped to another process This makes it easy to output a raw diff the changes between two versions of the file to a file but still allows you to see the colorized diff when you view the output directly Finally Git uses core editor to specify a particular editor Git launches an editor whenever you need to create a commit message edit patches and do a few other tasks Git doesn t require you to set the core editor value though It tries to figure out what editor to use by checking the following values in order EDITOR environment variable core editor configuration value VISUAL environment variable EDITOR environment variable and finally plain vi The value is the command line script to launch your editor In Windows this is a bit tricky but there s an excellent thread on Stack Overflow that can help you get started 11 http en wikipedia org wiki SHA 12 http j mp git editor on wind
95. m Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 How TO READ THIS BOOK well as some of the more complex ways to handle merging and moving branches around Part VI Working with the Repository History introduces you to all the history you ve been generating Using this information you can figure out what another developer or maybe even you was thinking when you made a particular change Part VIL Fixing Things shows you how Git can help you fix things in your repository be that commits that need to be adjusted or finding bugs in your code Part Moving Beyond the Basics introduces you to a few concepts that don t fit into the normal everyday workflow but are useful when they re needed There are diagrams throughout this book Whenever you see a circle it repre sents a commit with the exception of Figure 2 on page 16 where the circles represent repositories This matches the style used throughout the Git manual when it shows example repository structures to explain commands In addition to the standard graph ical diagrams throughout in some places I ve opted for a plain text diagram to introduce you to the Git manual diagram style Throughout the book you ll see examples of the output you can expect Git to generate for a given command Keep in mind that your output won t be exactly the same because of the way Git keeps track of commit IDs more on that in
96. mit on page 34 The changes are staged now it s time to commit them Task 7 Committing Changes on page 36 shows you how to create a commit and add a log message to it With any project files will be generated that you don t need to commit Task 8 Ignoring Files on page 38 teaches you how to tell Git to ignore those files What happens when you accidentally stage a file you didn t mean to or you decide that you want to get rid of a change that you made to a file before committing it Task 9 Undo ing Uncommitted Changes on page 40 covers how to undo those staged changes so you don t accidentally commit something Files sometimes need to change where they live A new pro ject layout is adopted or files or directories are renamed Task 10 Moving Files in Gif on page 42 shows you how to handle these inevitable changes Likewise some files or directories outlive their usefulness Since the repository keeps a record of all files that it has ever tracked you can delete those old files without worrying about not having them to reference later if you need to do so Task 11 Deleting Files in Git on page 44 shows you how Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 WORKING WITH GIT e Finally Task 12 Sharing Changes on page 46 is a whirlwind tour of how to share changes with other developers It s done at 30 000 feet and is enough to get you started A lo
97. mit if you ran git commit right now For more on committing flip to Task 7 Committing Changes on page 36 Files in this section show up as green if you turned colors on and are preceded by Changes to be committed Depending on the state of your repository the output from git status might contain any of those sections or none at all It adapts itself as needed ort erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing tober 2010 SEEING WHAT HAS CHANGED What the status of a new repository looks like If you just created a repository using git init this is what your repository looks like prompt git status f On branch master Initial commit nothing to commit create copy files and use git add to track What git status looks like in a repository with changes git status requires a repository with some changes in its working tree to see the various output The following is the output of git status on my local Castanaut repository Line 1 prompt git status f On branch master f Changes to be committed use git reset HEAD lt file gt to unstage 5 modified castanaut gemspec z Changed but not updated use git add lt file gt to update what will be committed 10 use git checkout lt file gt to discard changes in x modified README txt E f Untracked files 15 use git add file to in
98. n short circuit this with the no commit option This is useful when you want to review and possibly edit the changes from the merge before making a commit We touched on how Git attempts to merge commits in the introduction to Part III Fast forward merges are often useful but sometimes you want to log that a merge happened This is common in projects when a big feature that was developed in a separate branch is merged in it provides a single commit you can revert if it needs to be removed in the future You can do this with the no ff option It forces Git to create a merge commit showing that the two branches were merged Another extra you can add when merge commits are created is the log option Traditional merge log messages contain Merge branch development There are two ways you change this First you can add the log which adds the subject line from each commit to the merge commit message Or you can use m and a message which lets you specify the entire message just like git commit Git tries to figure out how to merge all the changes but sometimes it can t This is called a conflict and requires your intervention Task 24 Handling Conflicts on page 82 shows you how to handle these cases Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin MERGING COMMITS BETWEEN BRANCHES Merge changes from development to the master branch prompt git checkout master Switched to branch m
99. n specify multiple paragraphs by specifying multiple m parameters You can avoid git add and commit every change in your working tree with the a parameter It commits everything you have staged and all the changes to your working tree Because Git breaks committing and sharing into two separate tasks you can change commits that haven t been shared We ve all accidentally committed a file that we weren t supposed to and realized the second after we hit Enter that there was a problem with the commit You can amend your commit with the amend parameter You can add C HEAD HEAD points to the latest commit in your branch to the call to reuse the commit s original log message if you don t need to change it There s more on amend in Task 35 Fixing Commits on page 110 Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin COMMITTING CHANGES Stage and commit changes prompt git add some file prompt git commit m Some message master a276f08 Some message 1 files changed 2 insertions 0 deletions Commit all modified files prompt git commit m Some message a master 5d251db Some message 1 files changed 1 insertions 0 deletions Commit and launch editor for commit message prompt git add some file prompt git commit Related Tasks Task 5 Seeing What Has Changed on page 32 Task 6 Staging Changes to Commit on page 34 Task 12 Sharing Changes
100. n the next feature You realize a little while later that you could have implemented it in a cleaner fashion You could amend the commit see Task 35 Fixing Commits on page 110 if it s the last commit but since some time has elapsed you ve already created other commits This is where interactive rebasing comes into play Create the second commit with the fix you want to use and then launch git rebase i and pass it the commit ID of the original commit ID minus one For example if the commit ID was 322dafc you should use git rebase i 322dafc Git rebase s interactive mode launches your editor with a list of commits You can use the editor to move the last line the commit you just made up to immediately after the commit you want to merge it into then change the first word to say fixup to merge it into the original commit There five different options pick reword edit squash and fixup You can use any of these as the first word or the first letter of a line to adjust that commit when it is replayed Like a regular git rebase be careful how you rebase You can cause issues for other people who have synced off of your repository if you rebase code that you ve already shared Remember this simple rule of thumb don t rebase code you ve shared eport erratum Download from Wow eBook www wowebook com scopy is aiiis er 2010 this copy is P1 0 printin CONTROLLING HOW YOU REPLAY COMMITS Rebase in
101. nd iPod Beginning Mac Programming Develop with Objective C and Cocoa Tim Isted 300 pages ISBN 978 1934356 51 7 34 95 http pragprog com titles tibmac It s not an iPhone and it s not a laptop the iPad is a groundbreaking new device You need to create true iPad apps to take advantage of all that is possible with the iPad If you re an experienced iPhone developer iPad Programming will show you how to write these outstanding new apps while completely fitting your users expectation for this device iPad Programming A Quick Start Guide for iPhone Developers Daniel H Steinberg and Eric T Freeman 250 pages ISBN 978 19343565 7 9 34 95 http pragprog com titles sfipad Beginning Mac ogramming Develop with Objective C and Cocoa Tim Isted ited by Coleen Toporek iPad Programming A Quick Start Guide for iPhone Developers Daniel H Steinberg Eric T Freeman Bites by Collen 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 isit Us Onlin http pragprog com titles pg git Source code from this book errata and other resources Come give us feedback too Register for Updates http pragpro
102. ng N with the number of commits you want to display Often you need to see the changes made to the file in addition to the log message to fully understand the change You can use the p to show the diff the commit made ort erratum Download from Wow eBook wowebook com gt this copy is P1 0 printing r 2010 VIEWING THE LOG A View a reverse chronological list of all commits prompt git log commit 3ac20cfb09212f212a2f 60a6227610c680e8a95e Author Travis Swicegood lt development domain51 com gt Date Wed Aug 18 09 29 38 2010 0500 add sample output for Part V commit fa0016322bf4e73d1419ddc91777368db0 35484 Author Travis Swicegood lt development domain51 com gt Date Wed Aug 18 09 12 35 2010 0500 add in sample output for Part IV and so on and so on View the log with one shortened commit ID and subject prompt git log oneline 3ac20cf add sample output for Part V fa00163 add in sample output for Part IV 8bd724b add note about empty prompt to the intro and so on and so on View the last N commits prompt git log N examples prompt git log 5 show the last five prompt git log HEAD HEAD show the last five prompt git log 10 show the last ten prompt git log HEAD 10 HEAD show the last ten Show the changes made in the latest commit prompt git log 1 p HEAD Note that it is a 1 as in the number and not an as in library Related Tasks Ta
103. o code in a cave though Hoarding all your changes until they are just right is the quickest way to harm a project Share early share often git init creates a git directory in your current directory and initializes the Git repository inside that Once you ve initialized a repository you still need to add and commit the files using git add see Task 6 Staging Changes to Commit on page 34 and git commit see Task 7 Committing Changes on page 36 respectively but both of these require an initialized repository first You have to initialize the repository only once Once you ve initialized a repository you have a working tree that you can interact with The working tree is your view into what s stored in your repository It typically represents the latest copy of what s stored in your repository Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin CREATING A NEW REPOSITORY A Create a repository prompt mkdir some repository prompt cd some repository prompt git init For example to create a repository called widgets in the work directory use this prompt mkdir work widgets prompt cd work widgets prompt git init Initialized empty Git repository in work widgets git Create a repository in an existing directory and add all files from that directory prompt cd path to some directory prompt git init prompt git add prompt git commit m some commit message
104. ok www wowebook com scopy IS ai er 2010 this copy is P1 0 printin INITIALIZING BARE REPOSITORIES Initialize a bare repository prompt git init bare path to some repo git Initialized empty Git repository in path to some repo git Create a bare repository copy of a remote repository prompt git clone mirror remote repository example prompt git clone mirror work repo Cloning into bare repository repo git done Related Tasks Task 4 Creating a Local Copy of an Existing Repository on page 26 Task 19 Adding and Removing Remotes on page 70 Task 21 Retrieving Remote Changes Part II on page 74 Task 22 Sending Changes to Remotes on page 76 this copy is P1 0 pri Adding a caret to any commit name a commit ID branch name or tag tells Git to use that commit minus one You can add multiple carets HEAD means HEAD minus two and so on The tilde followed by a number is used with a commit name a commit ID branch name or tag to specify the commit located at that point minus the number HEAD 2 means two commits before HEAD and so on amend Applies the commit that is being made to the previous commit to amend it bare repository A repository without a working tree Generally used for repositories that are meant to be pushed and pulled to and from blame An annotated view of a file or portion of a file that shows what commit a change was made in w
105. om Wow eBook vw wowebook com gt this copy is P1 0 printin DELETING BRANCHES Delete a branch that has been merged into the current branch To delete a branch called experiment do this prompt git branch d experiment Deleted branch experiment was e9f9fdc Delete a branch that hasn t been merged into the current branch prompt git branch D experiment Deleted branch experiment was e9f9fdc Related Tasks Task 18 Tagging Milestones on the following page Report erratum Download from Wow this copy is P1 0 printi TAGGING MILESTONES Tagging Milestones You need to make milestones in your projects each slightly different such as for one its weekly iterations and for another its version numbers You can use git tag to handle this git tag creates a read only marker within the repository You can treat tags like branch names except you can t check them out and start committing to them You can create a new branch from a tag however Creating a tag requires one parameter the name of the tag Nearly every character you can use as part of a filename on Unix systems can be used as part ofa tag name You cannot use the characters or and a tag cannot begin or end with You can create a tag from a commit other than HEAD by supplying a second parameter to git tag It can be a reference commit either directly or relative to another commit or a branch name directly or rel
106. on page 46 Task 35 Fixing Commits on page 110 this copy is P1 0 pri IGNORING FILES 2 Ignoring Files Software projects generate a lot of cruft Some of it you don t need to commit For example I do a lot of work in Python which leaves a ton of pyc files laying around and I edit using MacVim which creates a swap file for each file that you re editing We don t need or want these files cluttering up our repository or showing up in git status That s where the gitignore and friends comes in Each line of the gitignore is scanned and any matches it finds are ignored by Git Your gitignore file is inside your repository so you can track it like any other file You can put it at the top level of your repository and in that case the rules cascade through all subdirectories You can also use subdirectory specific gitignore and those rules will only apply to files and directories inside that subdirectory Sometimes you don t want to commit your gitignore file to your repository Maybe you re be contributing to an open source project there s no need to add your swp to the project wide gitignore You have two options in this case use the git info excludes file or add the ignore cases to your global excludesfile The git info excludes is the same as a gitignore file except it s not tracked by Git since it s inside the git directory It s useful for excluding files that are specific to a project without adding a
107. opy is P1 0 printin ber 2010 TEMPORARILY HIDING CHANGES Stash the changes in your working tree prompt git stash Saved working directory and index state WIP on master 8e323b6 add meta tags HEAD is now at 8e323b6 add meta tags Apply a stash to the current working tree prompt git stash apply output looks similar to git status after apply Or to apply and remove from the stash use this prompt git stash pop same output as above plus Dropped refs stash 0 7649092 List the available stashes prompt gt git stash list stash 0 WIP on master 8e323b6 add lt meta gt tags Create a stash in patch mode prompt git stash save patch launches editor Delete stashes prompt git stash drop stash name Dropped stash 0 ea5bd0c Or to remove all stashed changes use this prompt gt git stash clear prompt gt Create a branch from an existing stash prompt gt git stash branch lt stash name gt Related Tasks Task 6 Staging Changes to Commit on page 34 Task 7 Committing Changes on page 36 Task 13 Creating and Switching Branches on page 54 Task 16 Rewriting History by Rebasing on page 60 this copy is P1 0 printi CHERRY PICKING COMMITS Cherry Picking Commits You sometimes need to grab one commit from another branch and merge it into your local branch such as a bug fix that needs to be backported You
108. ork 2b Pull changes from a remote repository prompt git pull remote name pull from a repository you cloned prompt git pull origin pull but rebase your local changes on top of the remote change instead of merging them prompt git pull rebase origin remote branch name 3 Push changes a remote repository prompt git push remote name branch name Related Tasks Task 4 Creating a Local Copy of an Existing Repository on page 26 Task 7 Committing Changes on page 36 Task 19 Adding and Removing Remotes on page 70 Task 20 Retrieving Remote Changes on page 72 Task 21 Retrieving Remote Changes Part II on page 74 Task 22 Sending Changes to Remotes on page 76 ort erratum TE TEN reves oa X load from Wow eBook om this copy is P1 0 printing r 2010 Part III Organizing Your Repository with Branches and lags ORGANIZING YOUR REPOSITORY WITH BRANCHES AND TAGS Now that you have the basics down it s time to learn about branches Branches allow you to segregate different lines of devel opment They re integral how Git works so having a good concep tual understanding of what they are is crucial to becoming profi cient with Git Version control systems of yesterday had poor support for branches and even worse support for merging those branches back together Git changes this In fact one of the most compelling features of Git is its ability to easil
109. otes Handling Remote Tags and Branches V Branches and Merging Revisited Task 24 Task 25 Task 26 Task 27 Task 28 Task 29 Handling Conflicts Handling Conflicts with a GUI Temporarily Hiding Changes Cherry Picking Commits Controlling How You Replay Commits Moving Branches Download from Wow eBook www wowebook com 46 48 54 56 58 60 62 64 66 70 72 74 76 78 80 82 84 86 88 90 92 CONTENTS Jl VI Working with the Repository s History 94 Task 30 Viewing the Log 98 Task 31 Filtering the Log Output 100 Task 32 Comparing Differences 102 Task 33 Generating Statistics About Changes 104 Task 34 Assigning Blame 106 VH Fixing Things 108 Task 35 Fixing Commits 110 Task 36 Reverting Commits 112 Task 37 Resetting Staged Changes and Commits 114 Task 38 Erasing Commits 116 Task 39 Finding Bugs with bisect 118 Task 40 Retrieving Lost Commits 120 VIII Moving Beyond the Basics 122 Task 41 Exporting Your Repository 124 Task 42 Doing Some Git Housekeeping 126 Task 43 Syncing with Subversion 128 Task 44 Initializing Bare Repositories 130 A Glossary 132 Index 136 Download from Wow eBook www wowebook com Like any book this is the result of much more than an author such as me sitting in front of their computer typing a bunch of words Please give me a few minutes to thank those involved in bringing this book to you First I d li
110. ou ve made it through these basic steps you ll be ready to start working with Git Feel free to skim the following tasks if you already have Git installed and configured and have created a new repository or cloned an existing one 3 promise no more get Git puns the rest of the book Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 GETTING STARTED INSTALLING GIT _ You can install Git in several different ways by using one of GUI installers by using a package management system or in the time honored Linux tradition that spawned Git by compiling it from source Don t worry if you re not ready to start compiling software all major operating systems provide alternatives to compiling Git yourself For example Ubuntu provides Git via its apt get tool so a few commands from the terminal are enough to get you going Likewise OS X users have the option of using MacPorts or the new Homebrew to handle the installation Not to be left out Windows users who use Cygwin can also install it via Cygwin s setup exe Windows and OS X users who prefer GUI installations have alternatives available as well Windows users can use the msysGit installer to get up and running and OS X users can install Git using the Git OS X Installer to install Git via a DMG The original way to install Git which is still the best if you want to remain on th
111. ows Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin CONFIGURING GIT Configure Git to know who you are prompt git config global user name Your Name prompt git config global user email user idomain com prompt Set the Git user for a specific repository prompt cd path to repository prompt git config user name Your Name prompt git config user email user idomain com prompt Turn colors on wherever possible in the Git UI prompt git config global color ui auto prompt Configure Git s editor prompt git config global core editor path to editor prompt M E VET e RC RE ONE Down vww woweboo this copy is P1 0 printing October 2010 CREATING A NEW REPOSITORY Creating a New Repository Repositories in Git are stored on your local file system right alongside the code they track You create a repository by typing git init in the directory that you want to start tracking files in You use two repositories in Git to collaborate with others a private one and a public one Your private repository the one we re creating here is where you do all your work It s the repository with the working tree This two tier system gives you the ability to track local experimental changes while only sharing changes via your public repository that are ready for others to work with Be careful that you don t allow yourself t
112. p experimentation in your own repository Online Resources Several online resources are available for this book The book s website is the jumping off point for all of them http pragprog com titles pg_git From here you can view the errata and add any errors you find and head to the book s forum where you can discuss and ask questions both about the book and about Git Now that you know what this book is about let s get started this copy is P1 0 printin Part Getting Started GETTING STARTED Ready to get started with Git Git is an extremely powerful tool that s relatively easy to start using Like all software it requires instal lation and minimal setup before you can start using it Covered in this part e We start off with Task 1 Installing Git on page 20 to handle installation Git s heritage in the Linux world means it can be compiled directly from source but there are other easier options for every major operating system You need to tell Git a few configuration settings before you start using it covered in Task 2 Configuring Git on page 22 Now that Git is installed and configured you start using it in Task 3 Creating a New Repository on page 24 You learn how to create a completely new repository e Another way to start a Git repository is to create a clone of someone else s repository covered in Task 4 Creating a Local Copy of an Existing Repository on page 26 Once y
113. p to speed quickly This book is for you if you re already familiar with another VCS such as Subversion and are looking for a quick guide to the Git landscape or if you re a quick study and want a concise guide It s organized by task to make it easy to translate from the task you need to accomplish to how the process works in Git If you ve never used a version control system before and thought Subversion was something you did to overthrow governments this book will get you up and running with Git For much more detail on version control concepts you should read Pragmatic Version Control Using Git my other book as well l http pragprog com titles tsgit How TO READ THIS BOOK How to Read This Book This book is organized in parts to guide you from starting out through more complex situations with each part broken down into tasks Tasks follow a specific formula the left page explains the task and the commands related to it and the right page gives you the raw commands with a little bit of informa tion about them and a cross reference to related tasks You can read this book in paper form as an open book to see the tasks side by side but it s also an excellent reference in digital form especially when searching for a particular Git task If you re reading a digital version of this book on a computer with a large enough display I recommend setting your reader to display two pages side by side instead of a single page Tha
114. parts Start with a one line subject that tersely describes the change that was made and then follow it with a more in depth body that describes the change in plain text The rule of thumb is to explain the change like you re explaining it to another developer Let the code speak for itself but make sure to include reasons for the change and explain any potentially odd choices Covered in this part e We start with the log in Task 30 Viewing the Log on page 98 You ll learn how to view the log in a couple of different formats and how to understand the information it displays e Once you understand the basics of querying Git s log Task 31 Filtering the Log Output on page 100 walks you through filtering those results through Git s revisions and ranges e Each commit tracks changes between files Those changes are described as diffs You ll learn how to view Git s diffs in Task 32 Comparing Differences on page 102 so you can see changes across different commits Everyone loves statistics Well at least managers do In addi tion to the excellent diffs and logs that Git provides it also gives you the ability to generate some statistics on the changes your repository is tracking You ll learn how to use Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 WORKING WITH THE REPOSITORY S HISTORY these tools in Task 33 Generating Statistics About Changes on page
115. positories other than your own local one repository The place where all your codes and the changes to it commits live revert A reverse commit used to track when a commit was undone revision A particular commit identified by a commit ID See commit and commit ID stage To add a one or more changes to the staging area to be commit ted staging area The place that sits between the repository and your work ing tree You must stage your changes here before they are committed to the repository port erratum Download from Wow eBook lt www wowebook com gt orintina October 2010 this copy is P1 0 printing iro e190 18 GLOSSARY stash To put all changes in the working tree into a temporary holding area to be reapplied or discarded later Useful when running rebase which requires a clean working tree tag A mark of significance within the repository when used as a noun The act of creating a tag when used as a verb working tree Your copy of a particular point in the repository s history normally the very last commit or HEAD that exists on the file sys tem This is where you edit the files in your project Report erratum ram Wowi om gt IDT EISE Down from Wow ntl this copy is P1 0 printing A A parameter staging files with 34 O parameter committing with 36 viewing branches with 56 abort parameter for rebasing 60 aborting conflicts
116. prefix parameter with a trailing slash when using git archive That tells Git to put the contents of the archive in its own directory within the archive so it s expanded into its own directory when you uncompress it git archive exports in either a tar format or a zip format You can specify which you prefer with format You can skip the format parameter if you provide either output or Git uses the file extension from the file provided to it to determine which type it should export You can also pipe the output through other commands to modify the output further if you don t use the output parameter The most common use is piping the output through gzip or bzip2 with gzip gt some file tar gz That turns the tar file into a gzipped tar file You can also pipe a zip file to gzip but that would be redundant and repetitive You can also export individual directories of your repository in addition to exporting the entire repository You do this by specifying the revision you want to export and adding a colon and the name of the directory you want to export 18 I really don t recommend doing that just in case the geek humor didn t make it through in print eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin ber 2010 EXPORTING YOUR REPOSITORY A Create a tar gz file of the latest changes in master prompt git archive format tar prefix my project latest HEAD
117. pull your changes in through a pull request Instead of an indicator of a project suffering from internal strife the num ber of forks on a repository is considered the sign of an active community working on a project The Git Workflow Working by yourself on a project with no version control you hack a little test it out and see whether it does what you want tweak a few more lines of code and repeat Adding version control into the mix you start committing those tweaks to keep a record of them The high level overview of Git s general workflow is shown in Figure 1 on the next page My Standard Workflow My standard day working with Git goes something like this I fetch all the changes from the other developers on my team to make sure I m working with the latest code and then I start working on the user stories I have for the day As I make changes I create a handful of commits a separate commit for each change that I make 2 http github com Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 THE GIT WORKFLOW Start your day here Make Changes amp Commit Them repeat until done Fetch Changes from the Team Share Changes with the Team Review Commits Figure 1 The Git workflow Occasionally I end up with several separate changes that all need to be com mitted break out Git s patch mode stage and finally commit each set of c
118. r moved around within the file and display that information prompt git blame C some file Related Tasks Task 30 Viewing the Log on page 98 Task 32 Comparing Differences on page 102 ort erratum TE TEN reves oa X load from Wow eBook om this copy is P1 0 printing r 2010 Part VII Fixing Things FIXING THINGS As we discussed earlier Git breaks the process of committing a change and sharing that same change into two separate proces ses The benefit of that separation comes into sharp focus when you need to fix something Every commit in Git can be changed You should avoid making changes to commits you ve shared to avoid potential conflicts with other developers Keeping that in mind you can adjust commits as much as you want Covered in this part e You need to fix a typo you forgot to run the unit tests before committing and accidentally broke them or you found a bug after the commit You learn how to fix these issues in Task 35 Fixing Commits on the next page e You can undo a commit after you ve shared your changes by reverting it applying the reverse of a commit as a new com mit You learn how to do this in Task 36 Reverting Commits on page 112 e You can reset your current HEAD to any other commit in the repository and start working from there In practice it s most useful to undo one or more of the most recent commits We cover this in Task 37 Resetting Staged Changes and
119. ranches 56 see also fetching pulling pushing cherry picking messages amending while merging 59 cherry picked commits 88 editing 88 112 merge log 58 reusing 36 110 stash 86 writing 36 95 metadata branch 54 milestones tagging 64 mixed parameter resetting with 114 moving branches 92 files directories etc 42 msysGit 20 multiple parameter fetching from remotes with 72 QD N option limiting log with 98 N parameter cherry picking with 88 pushing to Subversion repositories with 128 reverting with 112 naming bare repositories 130 branches 49 remote repositories 70 stash names 86 tags 64 no merged parameter viewing branches with 56 no commit parameter cherry picking with 88 merging with 58 reverting with 112 no edit parameter reverting with 112 no ff option merging with 58 non fast forward merges see recursive merges numstat parameter viewing statistics with 104 O parameter exporting with 124 oneline parameter viewing log with 98 onto parameter rebasing with 92 116 open source models 15 OS X installation 20 output parameter exporting with 124 overriding see forcing overwriting files 42 P p parameter staging files with 34 PATCH PARAMETER SUBVERSION viewing diffs in statistical output with 104 viewing log with 98 patch parameter stashing with 86 patches see diffs pick option in rebasing
120. rojects use a fully distributed model where only one person can push changes to the main repository and that person is responsible for merging changes from all the contributors into the main repository Having only one person capable of pushing changes is often too demanding a job for a large open source project Many have a main repository that all of the committers can send changes to The main developers encourage people who are just starting out to fork their project create a copy of the repository somewhere else so the main devel opers and other members of the community can review their changes If they re accepted one of the main contributors merges them back into the project s repository These different scenarios constitute different repository layouts Git allows several different layouts and covering them deserves a section to itself Repository Layouts The distributed nature of Git gives you a lot of flexibility in how you manage your repositories Every person on your team has their own private repository the repository that only that person can update However there are two distinct ways to handle public repositories For a visual explanation of these layouts see Figure 2 on the following page One method is the fully distributed model In this each developer has their own public repository that the developer uses to publish their changes to All the other developers on the team then pull changes from everyone el
121. rry Picking Commits on page 88 intro duces you to another way to pull individual changes from one branch into another We revisit the git rebase command in Task 28 Controlling How You Replay Commits on page 90 to learn how to use rebase interactively e You can move branches around There are several ways to do this depending on the circumstance Look at Task 29 Moving Branches on page 92 to see how Now let s brush up on our conflict resolution skills Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 HANDLING CONFLICTS Z Handling Conflicts You can t develop a project with other developers without generating conflicting versions of code from time to time Git goes a long way toward helping you resolve those automatically but sometimes it can t For example the code shown on the opposite page shows two different solutions to the same problem You must tell Git how to fix the conflict because it doesn t know which version is correct They both make changes to the exact same lines of code You can find out which file or files have conflicts in two ways the output from the failed git merge or git status You can find conflicts within a file by looking for lt lt lt lt lt lt lt seven lesser than signs with a commit such as HEAD The original code the code inside the branch you re merging into is located between the 7 lt and
122. rs Deliver Great Software Jonathan Rasmusson 275 pages ISBN 9781934356586 34 95 http pragprog com titles jtrap Dering Technical Chan Your co workers resistance to new technologies can be baffling on Learn to read users patterns of resistance Aand then dismantle their objections Every developer must master the art of evangelizing With these techniques and strategies you ll help your organization adopt your solutions without selling your soul to organizational politics Driving Technical Change Why People On Your Team Don t Act On Good Ideas and How to Convince Them They Should Terrence Ryan 200 pages ISBN 978 1934356 60 9 32 95 http pragprog com titles trevan The Agile Samurai How Agile Masters Deliver 4 Great Software A Jonathan Rasmusson ilte by Susannah Davidsen Patzer Driving Technical Change Why People On Your Team Don t Act on Good Ideas and How To Convince Them They Should Terrence Ryan Batted by Jacquelyn Carter Aimed at beginning developers without prior programming experience Takes you through concrete working examples giving you the core concepts and principles of development in context so you will be ready to build the applications you ve been imagining It introduces you to Objective C and the Cocoa framework in clear easy to understand lessons and demonstrates how you can use them together to write for the Mac as well as the iPhone a
123. rtions 176 deletions rewrite crank 81 create mode 100644 s index textile create mode 100644 s java textile Cherry pick but edit the commit message before committing prompt git cherry pick edit release 1 0 a oe ae prompt gt git cherry pick e release_1 0 Cherry pick but don t commit prompt git cherry pick no commit release 1 0 B wee OE prompt git cherry pick n release 1 0 Add a Signed off by line to the commit message prompt git cherry pick signoff release 1 0 wwe OF aes prompt git cherry pick s release 1 0 Related Tasks Task 7 Committing Changes on page 36 Task 15 Merging Commits Between Branches on page 58 report erratum n Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 CONTROLLING HOW YOU REPLAY COMMITS Controlling How You Replay Commits Rebasing in Git replays one set of commits on top of another We covered the basic case in Task 16 Rewriting History by Rebasing on page 60 There is an interactive mode to git rebase that lets you control how the commits are replayed Like a regular rebase git rebase i takes the commits in your current branch and replays them against another point in your repository s history You can use this to change the order of commits squash commits together or edit a previous commit Consider the following example You add a new feature and then start working o
124. ry without using a fast forward push but in those rare cases where it is necessary or desired you committed sensitive information or are removing a commit that does not need to be recorded for example you can use the force or f option to force Git to allow the update eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin ber 2010 SENDING CHANGES TO REMOTES Push the local tracking branch to your origin prompt git push Push first set of changes from master to your origin prompt git push origin master Push changes from a specific branch to a specific remote repository prompt git push remote name branch name example prompt git push tswicegood development Counting objects 42 done Delta compression using up to 2 threads Compressing objects 100 33 33 done Writing objects 100 42 42 39 49 KiB done Total 42 delta 18 reused 5 delta 4 Unpacking objects 100 42 42 done To git internal domain51 pvt sample repo git new branch development gt development For example to push to the production branch to the shared remote use this prompt git push shared production Push changes from the local master branch to the remote production branch prompt git push origin master production Force a remote branch to accept a push Warning Use this with extreme caution because it can cause others to get out of
125. s prompt git commit m Moved README into docs directory master 99a0de8 Moved README into docs directory 1 files changed 0 insertions 0 deletions rename README rst gt docs README rst 100 Related Tasks Task 6 Staging Changes to Commit on page 34 Task 7 Committing Changes on page 36 erratum Download from Wow eBook www woweb DELETING FILES IN GIT Deleting Files in Git Files and directories sometimes outlive their usefulness You can remove them from your working tree and tell Git to quit tracking them using the git rm command This doesn t remove the file from your repository s history it removes it only from your working tree going forward You can always go back in the history of the repository and see the files or directories that have been removed You call git rm and provide it with a filename to tell Git to remove it or a standard shell pattern php matches all files that end in php You don t have to provide the but it s necessary if you re trying to remove a file that conflicts with a command line option It tells Git that you re done providing options and everything else is a file You must provide the r option if you are deleting a directory and all the files under it It tells Git to recursively delete all the files starting at the provided directory Like most other actions in Git git rm requires git commit to finalize its action git rm stages the removal
126. s on page 82 and then continue You tell Git you re ready with git rebase continue You can also skip a commit that s causing a conflict by calling git rebase skip That could lead to further conflicts however You can abort the rebase too with git rebase abort There s always a safety net if you need to undo a rebase after it s completed Git points ORIG HEAD at the commit before major changes like git rebase are run You can use git reset to reset your repository back to that original state eport erratum Download from Wow eBook www wowebook com scopy IS er 2010 this copy is P1 0 printin REWRITING HISTORY BY REBASING Rebase your current branch against another For example rebase your current branch against master prompt git rebase master First rewinding head to replay your work on top of it Applying simple commit You can also rebase against a tag or commit ID For example if afOfe21 is the commit ID for master use this prompt git rebase af0fe21 same as above Undo a rebase after it completes prompt git reset hard ORIG HEAD HEAD is now at e9f9fdc update the README Using hard can be dangerous Check Task 37 Resetting Staged Changes and Commits on page 114 for an explanation of its use Before a Rebase ET master After a Rebase development master Related Tasks Task 15 Merging Commits Between Branches on page 58 Task 24
127. s using any range of revisions that work with git diff Adding any of the stat parameters tells Git to output the stats without showing the actual differences You can add p to the command to show both the statistical output and the patch or to show the differences We ve talked about viewing statistical information in the context of git diff but you can also view it from git log along with each log message Add stat shortstat or numstat to any git log command to add the respective statistical output to the log output ort erratum Download from Wow eBook www wowebook com SOODVIE ober 2010 this copy is P1 0 printing 2010 GENERATING STATISTICS ABOUT CHANGES Show change stats between the last ten commits prompt git diff stat HEAD 10 xcu aua prompt git diff stat HEAD 10 HEAD Show statistics between two commits prompt git diff stat first second example sr prompt git diff stat 423d021 1e85ac3 Show the number of files changed inserts and deletes in the last ten commits prompt git diff shortstat HEAD 10 Show stats in parseable format prompt git diff numstat HEAD 10 Show the patch in addition to the statistical information prompt git diff stat p HEAD Show statistics about commits in the log For full stats by file prompt git log stat To display cumulative stats only use this prompt git log shortstat
128. se s repositories to keep current In practice most teams have a lead developer who is responsible for making sure all the changes are integrated This limits the number of repositories you and your team have to pull changes from to one but it increases the workload on the person who has to integrate everyone s changes Another method is the shared repository model where all developers can push to a shared repository This resembles the standard centralized model and is often adopted by teams when they first start using Git it requires the least amount of mental overhead when it comes to thinking about where a change is shared You can mix both of these as well to create a hybrid solution Use a shared repository for all of the code that s ready for production and each developer maintains their own public repository for sharing code that s still a work in progress This is the model I ve employed successfully at my company and Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 ONLINE RESOURCES tul Bob Distributed Alice pository Repositories lt ie Lu 7 Push e y Bob You Alice Figure 2 Shared and distributed repository layout with three developers Gray circles are the private repositories outlined circles are public repositories that s used by many open source projects push final changes to the main repository and kee
129. sk 32 Comparing Differences on page 102 erratum Download from Wow eBook www wowebook com FILTERING THE LOG OUTPUT 4 100 S1 Filtering the Log Output Git s log is useful way to track what the original developer often yourself was thinking when they made a change but it often provides too much information You can use git log s many parameters to filter the results it displays zeroing in on the information that s important to you You can start to filter the results by providing Git with a directory or path You specify the path as the last parameter To be safe separate the path from other parameters with two dashes Otherwise Git can t tell the difference between the branch or tag work and the path work You can also filter the log based on the time of the commit Using the since or after parameter you can look at commits after a given point in time Git attempts to parse any string you give it but fails silently if it can t parse the date you provide Stick with traditional date and time formats or a number followed by months weeks days hours minutes and so on to make sure Git can understand you Git provides you with the opposite of since and after too you can use until or before to look for commits older than a given time You use author to filter the results by author or email address Git matches on a partial name author Travis match both commits I make and commits author
130. so on git checkout b new branch name HEAD is now at d7c8880 ignore stuff from virtualenv prompt git branch d master Deleted branch master was d7c8880 prompt git checkout b master Switched to a new branch master Related Tasks Task 4 Creating a Local Copy of an Existing Repository on page 26 Task 13 Creating and Switching Branches on page 54 Task 20 Retrieving Remote Changes on the following page Task 21 Retrieving Remote Changes Part II on page 74 Task 22 Sending Changes to Remotes on page 76 report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 RETRIEVING REMOTE CHANGES Retrieving Remote Changes You must keep your repository in sync with the changes from everyone else that is collaborating on it with you You do this with the git fetch command Fetching is closely related to git pull and many people incorrectly use the two commands interchangeably Fetching changes from a remote repository retrieves literally fetches the changes from that remote repository This stores them in their remote branches on your local repository You can use this to see what changes are on the remote repository without affecting your local repository Git fetches the changes from the origin remote repository if you don t specify a remote You can fetch from another repository by providing the name of that remote repository By default it fetches al
131. t Git is a bit different from traditional version control systems If you re com ing to Git from another centralized system this section explains some of the differences and gets you thinking in Git style Distributed vs Centralized There are generally two models in version control systems centralized and distributed Tools such as Subversion typically require a network connection to a centralized server You make a change to your project and then commit that change which is sent to the centralized server to track Other developers can then immediately access your changes Distributed version control systems such as Git break the process of com mitting code and sharing it with others into two parts You can commit your code to your local private repository without having to talk to a centralized server removing the need to be connected to a network to make a change Private vs Public Repositories Each developer who is sharing code with other developers has at least two repositories a private and a public repository The private repository is the one that exists on your computer and is the one you make commits to Public repositories are the repository that you use to share your changes with other developers Multiple developers might have access to push changes to the same public repository or each developer may have their own public repositories You can push to and fetch from multiple repositories This allows you to pull in
132. t First they ll never be perfect There s always something else to refactor and abstract away Second the bigger the change becomes the harder it becomes to fully understand review and test Third it makes tracking down bugs later easier Tools such as git bisect see Task 39 Finding Bugs with bisect on page 118 make finding which commit introduced a bug easy Smaller commits mean that once you know which commit caused the bug you can figure out The exact change that much faster We ve already covered how to create a new repository or clone an existing one git init and git clone in Task 3 Creating a New Reposi tory on page 24 and Task 4 Creating a Local Copy of an Existing Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing October 2010 WORKING WITH GIT Repository on page 26 respectively Making changes and testing are up to you and how you interact with the code in your project Seeing what changes need to be committed is where we pick up The tasks in this part are ordered roughly the same way you ll use them in Git Covered in this part The first thing is seeing what has changed We cover this in Task 5 Seeing What Has Changed on page 32 which shows you how to compare your working tree with what the repository knows about After you know what has changed then you need to stage the changes you want to commit This is covered in Task 6 Staging Changes to Com
133. t gives you the same visual that s intended in the book On your first pass I suggest that you read the introductions to each part They give you a broad overview of how to approach each part of the Git workflow as well as a synopsis of the tasks contained in that part Armed with high level information you can determine where to dive in You can read this book from start to finish or cherry pick the tasks relevant to what you re trying to accomplish The parts of this book are organized to walk you through the various phases of use in Git Part I Getting Started starts with the absolute basics installing and configuring Git and creating your first repository Part IL Working with Git covers the basic commands you need as part of your day to day interaction with Git by yourself These are the building blocks and they re a must read if this is your first time using Git Part Organizing Your Repository with Branches and Tags intro duces branches a powerful and central part of Git that s necessary for understanding how everything works together Part IV Working with a Team covers the most powerful aspect of any VCS collaborating with other developers This part gets you up to speed on how to share your work with other developers and retrieve changes from them Part V Branches and Merging Revisited builds on the information in Part III and teaches you how to handle it when things go wrong as Report erratu
134. t more about collaboration is covered in Part IV Working with a Team Now let s dive into the specifics this copy is P1 0 pri SEEING WHAT HAS CHANGED 2 Seeing What Has Changed Your local repository tracks changes Before you start committing just anything you need to see what changes exist between your working tree and your repository and what changes are staged and ready to commit git status is the tool for the job git status has several different outputs depending on what s in your working tree The example on the next page is from one of my repositories and it contains all three types of outputs staged changes changes to known files and untracked files Let s go over them in reverse order of how they appear on the next page the order of least important to most Starting at lines 14 and ending at 17 Git outputs the files and paths that it doesn t know anything about the files that you haven t told Git about yet This section has the header Untracked files before it starts and if you turned on color output like we discussed in Task 2 Configuring Git on page 22 it displays the files and paths in red Next up are the files that Git knows about but that have changed These are listed between lines 8 and 12 and are preceded by Changed but not updated Like untracked files these show up as red if you have colors configured Finally the top section listed between lines 3 and 6 shows what files you would com
135. tash save Providing the save option allows you to specify a message explaining what the stash was There are two commands to apply previous stashes to your current working tree apply and pop You can use apply to make the change to your working tree without removing the stashed change from your stash Most of the time you want to apply it and remove it from the stash though That s where pop comes in It pops the change off the stack and applies it Creating stashes stores the commits outside of normal branches To see what stashed changes are available you can use the git stash list command Like the name hints at it lists all the stashed changes You can use the patch parameter to stash a portion of the change It works just like git add p see Task 6 Staging Changes to Commit on page 34 Sometimes you create a stash and then realize you don t need it any longer You can use git stash drop stash name to delete an individual stash or you can use the clear option to remove all the stashed changes Another interesting use of git stash is the branch option You can use it to create a new branch from a stash Git creates a new branch for you that looks exactly like your repository did when you called git stash originally This is useful for applying a stash to see its changes in situations where the stash does not apply cleanly to the current working tree eport erratum Download from Wow eBook www wowebook com this c
136. teps with this prompt make all doc prompt make install install doc Install Git on Ubuntu prompt sudo apt get install git core To install the user manual do this prompt sudo apt get install git doc To install the Git to Subversion functionality do this prompt sudo apt get install git svn You can use apt get to handle all of the dependencies and then compile Git from source using the previous steps prompt sudo apt get build dep git core git doc git svn Install Git on OS X You can use MacPorts and install Git with SVN functionality prompt sudo port install git core There is also a Git Installer for OS X available on Google Code Install on Windows Download latest msysGit installer from here http code google com p msysgit Or install as part of Cygwin s setup process 10 http git scm com Download from Wow eBook www wowebook com CONFIGURING GIT Configuring Git Git requires some configuration to work You must tell Git your name and your email address since there is no central repository to keep track of that information Git uses both to calculate the commit ID an SHA 1 hash that identifies each commit The first two commands on the next page use global to specify that they are configuration values for every repository you interact with on this machine The configuration file is stored in gitconfig You can edit the file direct
137. ter with amrnend when you want to reuse the original commit message You can use git rebase i to replay the history of your repository and stop at certain points Run the command provide it with the parent of the commit you want to edit and then mark that commit as edit Git stops at that point and then lets you work on your repository as if it were the previous commit see Task 28 Controlling How You Replay Commits on page 90 You can fix typos remove some buggy code or do anything else you would normally do with the previous commit Then call git rebase continue so Git can finish rebasing the rest of the history It s worth noting again be careful when rewriting history Feel free to rewrite to your heart s content until you share your work After that only rewrite when you have no other option available Download from Wow eBook lt www wowebook com gt this copy is P1 0 printin FIXING COMMITS Amend the previous commit Make the changes you want and stage those changes and then use this prompt git commit amend launch editor x _ Amend the previous commit and keep the same log message prompt git commit amend C HEAD master 38ec64e update the README 1 files changed 5 insertions 0 deletions Fix the previous commit by removing it entirely prompt git reset hard HEAD HEAD is now at 68 3164 use json if available Use interactive rebase to edit a commit other than t
138. teractively prompt git rebase i amp lt commit ID example prompt git rebase i HEAD 5 For example to interactively rebase the last five commits use this prompt git rebase i HEAD 5 or prompt git rebase i HEAD See an example interactive rebase The following is the result of a git rebase i on one of my projects pick 6024857 remove theme from repo pick 29e2376 add in dependency on external repo for theme pick 7ce4bdf add code to handle deployment of new docs Rebase 86968d5 7ce4bdf onto 86968d5 Commands p pick use commit r reword use commit but edit the commit message e edit use commit but stop for amending S squash use commit but meld into previous commit f fixup like squash but discard this commit s log message If you remove a line here THAT COMMIT WILL BE LOST However if you remove everything the rebase will be aborted Related Tasks Task 15 Merging Commits Between Branches on page 58 Task 16 Rewriting History by Rebasing on page 60 rt erratum NAIM AREA Atala SENS Download from Wow WWW WOWeb this copy is P1 0 printing October 2010 MOVING BRANCHES Moving Branches Sometimes you need to move branches around to reorganize them For example you have a branch where you re working on a future version of your software During the rewrite your team realizes that the better widg
139. th that introduces the bug once you ve found the commit and figured out how to address it run the following to return back to the branch you started at prompt git bisect reset Use a shortcut to start bisect with HEAD being bad prompt git bisect start HEAD some good commit id continue as above Use an automated script to test commits prompt git bisect start HEAD some good commit id prompt git bisect run path to test script once you ve figured out the fix prompt git bisect reset Find a bug in the history with bisect The commit to the right is HEAD and the commit to the left is known to be good git bisect cuts the repository in half and through a process of elimination shows that HEAD is the commit that introduced the bug Now imagine there were 100 commits separating HEAD and the last known good commit Bisect Starts Here Marked as Good The bad commit is introduced here Known Good Known Bad Related Tasks Task 30 Viewing the Log on page 98 Task 32 Comparing Differences on page 102 Task 34 Assigning Blame on page 106 ort erratum minar iA esee E n ank a NU FX EN Jownload from Wow JOK CO this copy is P1 0 printing ber 2010 RETRIEVING LOST COMMITS 120 0 Retrieving Lost Commits Rebasing commits causes the history of your repository to change Ever wonder what happens if you accidentally delete the wrong commit in an interactive rebase
140. then commit them into your local branch as one commit Remember to start with the oldest commit first when cherry picking more than one commit otherwise you might end up trying to make a change that isn t possible or having conflicts because it is in the wrong order You can also add a Signed off by line to the end of a cherry picked commit Signed off lines consist of the phrase Signed off by followed by your name and email address pulled from the configuration This is useful for creating a chain of review for commits and can become essential in backported commits to ensure they have been properly reviewed prior to being merged into an existing branch eport erratum Download from Wow eBook www wowebook com this copy is P1 0 printin ber 2010 CHERRY PICKING COMMITS Merge a single commit from another branch into your local one prompt git cherry pick some commit ID some commit ID refers to a commit any way you normally can an actual commit ID branch name tag or some relative version of any of those For example to cherry pick the latest from release 1 0 or commit a74cc83 use this prompt git cherry pick release 1 0 Finished one cherry pick master bcdbca8 add meta tags 1 files changed 1 insertions 0 deletions prompt git cherry pick a74cc83 Finished one cherry pick master dd94f18 working on conerting to Textile Author Andy Lester lt andy petdance com gt 5 files changed 195 inse
141. tic Guide to 2010 9781934356593 300 Learning Programming Languages Ship It A Practical Guide to Successful Software Projects 2005 9780974514048 224 SQL Antipatterns Avoiding the Pitfalls of Database 2010 9781934356555 352 Programming Stripes and Java Web Development Is Fun Again 2008 9781934356210 375 Test Drive ASPNET MVC 2010 9781934356531 296 TextMate Power Editing for the Mac 2007 9780978739232 208 The Agile Samurai How Agile Masters Deliver Great 2010 9781934356586 280 Software The Definitive ANTLR Reference Building 2007 9780978739256 384 Domain Specific Languages The Passionate Programmer Creating a Remarkable 2009 9781934356340 200 Career in Software Development ThoughtWorks Anthology 2008 9781934356142 240 Ubuntu Kung Fu Tips Tricks Hints and Hacks 2008 9781934356227 400 Web Design for Developers A Programmer s Guide to 2009 9781934356135 300 Design Tools and Techniques More Languages n Languages in Seven Week In this book you ll get a hands on tour of Clojure Haskell Io Prolog Scala Erlang and Ruby Whether or not your favorite language is on that list you ll broaden your perspective of programming by examining these languages side by side You ll learn something new from each and best of all you ll learn how to learn a language quickly Seven Languages in Seven Weeks A Pragmatic Guide to Learning Programming Languages Bruce A Tate 300 pages ISBN 978 1934356 59 3 34 95 http pragprog com
142. titles btlang Language Implementation Pattern Learn to build configuration file readers data readers model driven code generators source to source translators source analyzers and interpreters You don t need a background in computer science ANTLR creator Terence Parr demystifies language implementation by breaking it down into the most common design patterns Pattern by pattern you ll learn the key skills you need to implement your own computer languages Language Implementation Patterns Create Your Own Domain Specific and General Programming Languages Terence Parr 350 pages ISBN 978 1934356 45 6 34 95 http pragprog com titles tpdsl Seven Languages in Seven Weeks A Pragmatic Guide to Learning Programming Languages Bruce A Tate Batted by Jacquelyn Carter Edited by Susannah Davidson Plater Language Implementation Patterns Create Your Own Domain Specific and General Programming Languages Terence Parr If you re programming applications that store data then chances are you re using SQL either directly or through a mapping layer But most of the SQL that gets used is inefficient hard to maintain and sometimes just plain wrong This book shows you all the common mistakes and then leads you through the best fixes What s more it shows you what s behind these fixes so you ll learn a lot about relational databases along the way SQL Antipatterns Avoiding the Pitfalls of Datab
143. w branch master tswicegood master Fetch a specific branch This requires a peculiar refspec to make sure the fetched branch ends up in the right place in your local repository prompt git fetch remote local branch remotes remote remote branch To fetch master from origin to your local copy of the origin master remote branch use this prompt git fetch origin master remotes origin master Fetch changes from multiple remote repositories prompt git fetch multiple remotel remote2 and so on Fetch changes from all remote repositories prompt git fetch all example after adding another remote prompt git fetch all Fetching tswicegood Fetching petdance remote Counting objects 414 done remote Compressing objects 100 161 161 done remote Total 407 delta 231 reused 397 delta 227 Receiving objects 100 407 407 52 53 KiB done Resolving deltas 100 231 231 completed with 2 local objects From http github com petdance bobby tables new branch master petdance master Related Tasks Task 4 Creating a Local Copy of an Existing Repository on page 26 Task 19 Adding and Removing Remotes on page 70 Task 21 Retrieving Remote Changes Part II on the next page Download from Wow eBook lt www wowebook com gt RETRIEVING REMOTE CHANGES PART II Retrieving Remote Changes Part II Many people new to Git treat git fetch and git pull as synonyms
144. with Git 14 A Mac only clone of Gitk that is designed to be more Mac like It s available from http gitx frim nl Report erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing ber 2010 VIEWING BRANCHES View all local branches prompt git branch master new newer newest View all remote branches prompt git branch r origin master View all branches prompt git branch a master new newer newest remotes origin master View all that are or are not merged into the current branch prompt git branch merged prompt git branch no merged View all branches that contain a particular commit prompt git branch contains commit id Related Tasks Task 13 Creating and Switching Branches on page 54 Task 15 Merging Commits Between Branches on the next page this copy is P1 0 pri MERGING COMMITS BETWEEN BRANCHES Merging Commits Between Branches You have to merge changes from another branch into your current branch in order to be able to use them The simplest way to do this is through git merge git merge takes two options the name of the other branch you want to merge and the optional local branch you want to merge into You can leave off the current branch when you re merging changes into your current branch By default git merge commits the merged changes if they can be successfully merged You ca
145. y handle creating branches and gracefully merge them back together Branches track changes to multiple versions of a project For exam ple you might be finishing up version 1 0 and already starting on new features for version 1 1 Using branches you can keep the code from version 1 0 isolated so new features from 1 1 don t accidentally slip into the version that is getting ready to release You give branches names making it easier track them based on their name rather than some commit ID master is the name of the default branch that Git uses All your commits so far in this book have been in that branch You can create as many branches as you want Branches Git are relatively simplistic they re simply a text file in side the repository that marks the latest commit in the branch Treat ing branches as pointers makes operations with branches painless and fast There are several different ways to approach using branches One approach is the topic branch You can use this style of branch to work on a specific feature fix a bug or deal with any other topic Once it s complete then you merge the finished changes back into your master branch Another common type of branch is the release branch the type of branch mentioned earlier You create release branches as you approach a release in your project They re useful when you or other members on your team are working on multiple versions of your project You can create a branc
146. y of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks Where those designations appear in this book and The Pragmatic Pro grammers 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 The team that produced this book includes Editor Susannah Davidson Pfalzer Indexing Potomac Indexing LLC Copy edit Kim Wimpsett Layout Steve Peter Production Janet Furlow Customer support Ellie Callahan International Juliet Benda Copyright 2010 Pragmatic Programmers LLC rights reserved No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photocopying recording or otherwise without the prior
147. your commits in the repository and special remote branches track which commits have branches pointing to them You can treat remote branches like normal branches with one ex ception you can t commit to them That means you can merge or cherry pick commits from them into your local branches or rebase eport erratum Download from Wow eBook lt www wowebook com gt this copy is P1 0 printing ober 2010 WORKING WITH A TEAM your local branches on top of remote branches The only way to get commits into a remote branch is to push those changes to the remote Covered in this part e First you need to know how to handle remote repositories You learn that in Task 19 Adding and Removing Remotes on the next page e Next up is fetching changes from remote repositories which you learn about in Task 20 Retrieving Remote Changes on page 72 After you know how to fetch changes we go over the short hand command for fetching and merging changes at the same time in Task 21 Retrieving Remote Changes Part Il on page 74 Grabbing changes from other developers is only half the pro cess You need to be able to send your changes back out into the world Task 22 Sending Changes to Remotes on page 76 shows you how e We ve already talked about tags and branches locally You learn about remote tags in Task 23 Handling Remote Tags and Branches on page 78 Before you start concerning yourself with pushing and pulling how ev
148. your project into different areas is useful only if you can merge the changes all back together You learn this in Task 15 Merging Commits Between Branches on page 58 No coverage of merging is complete without talking about rebasing Rebasing is often misunderstood and feared so Task 16 Rewriting History by Rebasing on page 60 gets you com fortable with the mechanics of rebasing ort erratum Download from Wow eBook www wowebook com this copy is P1 0 printing ober 2010 ORGANIZING YOUR REPOSITORY WITH BRANCHES AND TAGS e Branches often outlive their intended use Once you no longer need a branch you can then delete it using the methods de scribed in Task 17 Deleting Branches on page 62 e Finally you need to be able to mark milestones in your branches We cover that in Task 18 Tagging Milestones on page 64 At first glance it might seem odd that branches generally consid ered an advanced topic in most version control systems are cov ered before discussing how to collaborate with a team There is a reason for this Remotes in Git are read only branches Once you know how to work with a branch you know how to interact with a remote repository minus a couple of extra commands we ll cover when we get there ort erratum Jownload from Wow eBook w book com gt this copy is P1 0 printing ber 2010 CREATING AND SWITCHING BRANCHES Creating and Switching Branches Git s branches enable you

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