Git The fast version control system Jeroen Rosenberg @jeroenrosenberg

Table of contents  Short introduction to version control  Version control systems  Comparison with subversion  Distributed version control  Git usage  Basic operations  Solving conflicts  Branching as a core concept  Tooling  Conclusion Git - the fast version control system

Version control Short introduction Git - the fast version control system

Version control (1)  The management of changes to documents, programs, and other information stored as computer files  A system that maintains versions of files at progressive stages of development.  Every file  Has a full history of changes  Can be restored to any version  A communication tool, like email, but with code rather than human conversation Git - the fast version control system

Version control (2)  Benefits Git - the fast version control system

Version control (2)  Benefits  Allows a team to share code Git - the fast version control system

Version control (2)  Benefits  Allows a team to share code  Maintains separate “production” versions of code that are always deployable Git - the fast version control system

Version control (2)  Benefits  Allows a team to share code  Maintains separate “production” versions of code that are always deployable  Allows simultaneous development of different features on the same codebase Git - the fast version control system

Version control (2)  Benefits  Allows a team to share code  Maintains separate “production” versions of code that are always deployable  Allows simultaneous development of different features on the same codebase  Keeps track of all old versions of files Git - the fast version control system

Version control (2)  Benefits  Allows a team to share code  Maintains separate “production” versions of code that are always deployable  Allows simultaneous development of different features on the same codebase  Keeps track of all old versions of files  Prevents work being overwritten Git - the fast version control system

Glossary Some commonly used terms explained before moving on Git - the fast version control system

Key terms in version control   Branch a copy of a set of files under version control which may be developed at different speeds or in different ways   Checkout to copy the latest version of (a file in) the repository to your working copy   Commit to copy (a file in) your working copy back into the repository as a new version   Merge to combine multiple changes made to different working copies of the same files in the repository   Repository a (shared) database with the complete revision history of all files under version control   Trunk the unique line of development that is not a branch   Update to retrieve and integrate changes in the repository since the update.   Working copy your local copies of the files under version control you want to edit Git - the fast version control system

Version control systems Git - the fast version control system

Very limited and inflexible Concurrent Versions System (CVS) Git - the fast version control system

Very limited and inflexible Concurrent Versions System (CVS) Fills most of the holes found in CVS, but added nothing to its development model Subversion (SVN) Git - the fast version control system

Very limited and inflexible Concurrent Versions System (CVS) Fills most of the holes found in CVS, but added nothing to its development model Subversion (SVN) More feature rich and functional Git Git - the fast version control system

Comparison with SVN Subversion Git Git - the fast version control system

Comparison with SVN Subversion  Centralized Git  Distributed Git - the fast version control system

Comparison with SVN Subversion  Centralized  Branching can be a pain and is used sparingly Git  Distributed  Branching is very easy and is a core concept Git - the fast version control system

Comparison with SVN Subversion  Centralized  Branching can be a pain and is used sparingly  Conflicts frequently occur and renaming is not handled well Git  Distributed  Branching is very easy and is a core concept  Conflicts occur less frequent, renaming is properly handled Git - the fast version control system

Comparison with SVN Subversion  Centralized  Branching can be a pain and is used sparingly  Conflicts frequently occur and renaming is not handled well  Can be slow due to network latency Git  Distributed  Branching is very easy and is a core concept  Conflicts occur less frequent, renaming is properly handled  Very fast since less operations involve network latency Git - the fast version control system

Comparison with SVN Subversion  Centralized  Branching can be a pain and is used sparingly  Conflicts frequently occur and renaming is not handled well  Can be slow due to network latency  Can consume quite some disk space Git  Distributed  Branching is very easy and is a core concept  Conflicts occur less frequent, renaming is properly handled  Very fast since less operations involve network latency  Consumes 30 times less disk space Git - the fast version control system

Distributed version control The new generation of version control Git - the fast version control system

A basic, centralized version control system Users commit changes to the central repository and a new version is born to be checked out by other users Git - the fast version control system

A distributed version control system Each user has a full local copy of the repository. Users commit changes and when they want to share it, the push it to the shared repository Git - the fast version control system

Git usage Basic operations Git - the fast version control system

Tracking a project.. SVN Git $ svn checkout url $ git clone url Git - the fast version control system

Tracking a project.. SVN Git $ svn checkout url $ git clone url origin/ master doc src … master doc src … Mirror the central server Anything the main repository can do, you can do! Git - the fast version control system

Tracking a project.. SVN Git $ svn checkout url $ git clone url My project is tiny - git is overkill “Why would I carry a Swiss knife when I only want to open cans?” Git - the fast version control system

Tracking a project.. SVN Git $ svn checkout url $ git clone url Tiny projects should be scalable too! “You wouldn’t use Roman digits just because you perform calculations with small numbers, now would you?” Tiny projects may grow beyond your expectations “One day you’ll desperately need that hex wrench and you’re stuck with your plain can- opener” Git - the fast version control system

Tracking a project.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file $ svn rm file $ git rm file $ svn mv file $ git mv file $ svn commit $ git commit –a $ svn revert path $ git checkout path Pretty straightforwarded, huh? Git - the fast version control system

Advanced committing… SVN Git … … $ svn mv file $ git mv file $ svn commit $ git commit –a $ svn revert path $ git checkout path What if you screw up? # re-edit the metadata and update the tree $ git commit --amend or # toss your latest commit away without changing the working tree $ git reset HEAD^ Git - the fast version control system

Solving conflicts Instant merging Git - the fast version control system

Closer look at pulling.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … Git - the fast version control system

Auto-merging.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … What actually happens… # Fetch latest changes from origin $ git fetch # Merge fetched changes into current branch $ git merge refs/heads/master Git - the fast version control system

Auto-merging.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … What actually happens… Recursive merge strategy – create a merged reference tree of common ancestors for three-way merge   fewer merge conflicts   can detect and handle renames Git - the fast version control system

Resolving conflicts.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … Suppose Jeff and Dan both made changes to the same line in file… CONFLICT (content): Merge conflict in file Automatic merge failed; fix conflicts and then commit the result. Uh oh…. now what? Git - the fast version control system

Resolving conflicts.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … Well, just merge manually… # run your favourite file merge application $ git mergetool –t opendiff Git - the fast version control system

Git - the fast version control system source: http://gitguru.com

Resolving conflicts.. SVN Git $ svn checkout url $ git clone url $ svn update $ git pull $ svn add file $ git add file … … …and commit! # commit to resolve the conflict $ git commit Git - the fast version control system

Branching A core concept Git - the fast version control system

Creating a branch.. SVN Git $ svn copy url_of_trunk url_of_branch $ svn switch url_of_branch $ git branch name_of_branch $ git checkout name_of_branch Git - the fast version control system

Creating a branch.. SVN Git $ svn copy url_of_trunk url_of_branch $ svn switch url_of_branch $ git branch name_of_branch $ git checkout name_of_branch Or create and switch to a branch based on another branch $ git checkout –b new_branch other_branch Git - the fast version control system

Some common scenarios… Git - the fast version control system Why would I require branching?

Scenario 1 – Interrupted workflow You’re finished with part 1 of a new feature but you can’t continue with part 2 before part 1 is released and tested Git - the fast version control system

Scenario 1 – Interrupted workflow • $ git checkout –b part2 Work on part 2 • $ git checkout master • Fix part 1… • $ git checkout part2 • $ git merge master Part 1 is approved • $ git checkout master • $ git merge part2 • $ git branch –d part2 Feature finished You’re finished with part 1 of a new feature but you can’t continue with part 2 before part 1 is released and tested Git - the fast version control system

Scenario 2 – Quick fixes While you’re busy implementing some feature suddenly you’re being told to drop everything and fix a newly discovered bug Git - the fast version control system

Scenario 2 – Quick fixes • $ git commit –a • $ git checkout –b bugfixbranch SHA1_HASH Fixed bug • $ git commit –a –m “Fixed bug” • $ git push • $ git checkout master Resume work While you’re busy implementing some feature suddenly you’re being told to drop everything and fix a newly discovered bug Git - the fast version control system

Git usage overview Just to summarize… Git - the fast version control system

Git command sequence Source: http://git.or.cz Git - the fast version control system

Tooling Stuck at ‘Ye Olde Terminal’? Not necessarily… Git - the fast version control system

Git UI front-ends • Comes with command-line client • Looks quite ugly, but does the job • Acts as a reference Gitk • Comes with command-line client • UI more appealing than gitk • Functionality Git Gui • OS X port of Git Gui • Looks quite nice • Still lacks functionality GitX Git - the fast version control system

  OpenInGitGui Git - the fast version control system Finder extension

  OpenInGitGui Git - the fast version control system Finder extension   TortoiseGit   Git Extensions Windows Explorer extensions

  OpenInGitGui Git - the fast version control system Finder extension   TortoiseGit   Git Extensions Windows Explorer extensions   JGit / EGit Eclipse integration

Conclusion Why switch to Git? Git - the fast version control system

Reasons to switch to Git  Endless, easy, non-file-system-based, local branches  Enhanced merging strategy  Performance  Advanced features enable better workflow  Stashing temporary work  Collaboration before public commits Git - the fast version control system

Closing and Q&A  References  Git: http://git-scm.com/download  Git Docs: http://git-scm.com/ documentation  GitX: http://gitx.frim.nl/  TortoiseGit: http://code.google.com/p/ tortoisegit/  Git Extensions: http://sourceforge.net/ projects/gitextensions/  JGit / EGit: http://www.eclipse.org/ egit/ Git - the fast version control system