Git - Speaker Deck

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jnewland.com/tag/git

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What is Git? • A popular distributed version control system designed to handle very large projects with speed and efﬁciency. • http://git.or.cz/

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quick survey • Who is not using source control? • SVN? • CVS? (still?)

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• Written by Linus Torvalds • Written to manage the Linux Kernel Git History

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Getting Git

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For the brave # install gnupg, gettext $ curl -O http://kernel.org/pub/software/scm/git/ git-1.5.4.1.tar.gz $ tar xzf git-1.5.4.1.tar.gz $ ./configure $ make $ sudo make install $ curl http://www.kernel.org/pub/software/scm/git/git- manpages-1.5.4.tar.bz2 $ sudo tar xjf git-manpages-1.5.4.tar.bz2 -C /usr/ local/share/man

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For the weak sudo port install git-core +svn sudo apt-get install git-core sudo yum install git-core

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Initial Setup $ git config --global user.name='My Name' $ git config --global user.email=me@mydomain.net # optional, for pretty colors $ git config --global color.diff=auto $ git config --global color.diff.new=cyan $ git config --global color.diff.old=magenta $ git config --global color.diff.frag=yellow $ git config --global color.diff.meta=green $ git config --global color.diff.commit=normal

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Why Git? • Distributed, not Centralized • Revolutionizes how you use branching • Extremely stupidly ridiculously fast, even with large projects • Community

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Centralized vs Distributed

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Centralized VCS • Repository • History stored in central location • Checkout • A ‘working tree’

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Distributed VCS • Every Git working directory is a full-ﬂedged repository with full revision tracking capabilities, not dependent on network access or a central server. • Commits happen ofﬂine. • Commits can then be pushed and pulled between repositories with shared history.

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Wait, commits happen ofﬂine?

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Commits happen ofﬂine!!!!!!!11!!!

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on the plane

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on the train

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at that crappy coffee shop with the paid WiFi

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at an ATLRUG meeting

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Branching FTW

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“But I don’t branch”

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because you don’t use Git

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quick survey #2 • How many of you use branching? • Work exclusively on trunk/master? • NEVER work on trunk/master?

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Why branching with Git is awesome • Instant $ time git checkout -b newbranch Switched to a new branch "newbranch" real 0m0.227s • Private • Merging doesn’t suck

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Forget about ‘breaking the build’ • ‘Atomic’ commits are a thing of the past • ‘Atomic’ merges

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• Prototype well-developed changes • Commit early and often • Review and revise before you merge Topic Branches

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With Git, branches are now a part of my everyday workﬂow

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‘Tomorrow’ branch

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‘Drunk’ branch

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Performance

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Offline Operations • Performing a diff • Viewing file history • Committing changes • Merging branches • Obtaining any other revision of a file • Switching branches

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Online operations are fast too $ time svn co http://svn.rubyonrails.org/rails/ trunk/ ... real 0m29.537s

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Online operations are fast too $ time git clone --depth 1 git://github.com/josh/ rails.git ... real 0m9.088s

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Online operations are fast too $ time git clone git://github.com/josh/rails.git ... real 0m37.512s

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Git for Subversion Users

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This looks familiar $ git status $ git log $ git blame $ git add FILE $ git rm FILE $ git mv FILE $ svn status $ svn log $ svn blame $ git add FILE $ git rm FILE $ git mv FILE

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Creating a Repo $ pwd ~/src/foo $ git init $ git add . $ git commit

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Checking out a Repo $ git clone REPO_URL

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git status • Untracked Files • Brand new ﬁle • Changed but not updated • Locally changed ﬁle not in the index • Changes to be committed • ‘The Index’

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The Index • Staging area for your next commit • Sort of like ﬁles marked A, M, D in svn status output

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One major difference • After making any changes to the working directory, and before running the commit command, you must use the add command to add any new or modiﬁed ﬁles to the index.

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Example # create bar and to the index echo “foo” > bar git add bar # change bar, and thus remove from the index echo “ “ >> bar # add bar to the index again git add bar

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Committing • git commit • commit what’s in the index • git commit -a • adds changed but not untracked ﬁles to the index, then commits • exactly like SVN

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Diffs # diff between working tree and the index $ git diff # diff between the index and last commit $ git diff --cached # diff between working tree and last commit $ git diff HEAD

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Logs # just like svn $ git log # find a commit changed a specific string $ git log -S"def stupid_method" # log with patches for each commit $ git log -p

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Reverting Changes $ git checkout PATH $ svn revert PATH

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git revert != svn revert # most similar to svn revert $ git checkout . # reverse commit and commit the result $ git revert

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Branching # create a new branch $ git branch NEW_BRANCH # switch to this branch $ git checkout NEW_BRANCH # create a new branch and check it out in one step $ git checkout -b NEW_BRANCH

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More Branching # view available branches $ git branch * new_branch master # delete a branch $ git branch -d ALREADY_MERGED_BRANCH $ git branch -D BAD_BRANCH

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Difﬁng and Logging with Branches # log of changes to other_branch not in master $ git log NEW_BRANCH..master # diff of those changes $ git diff NEW_BRANCH..master

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Merging # get back to the master $ git checkout master # merge in changes from your other branch $ git merge NEW_BRANCH # optionally, delete the branch $ git branch -d NEW_BRANCH

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Rebasing # store local changes not in BRANCH_NAME as patches, updates the local branch to BRANCH_NAME, then applies the patches $ git rebase BRANCH_NAME

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Danger, Will Robinson • Rebase is dangerous • Rewrites commit history • Don’t use on a branch you’re sharing

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Oh noes! Merge Conﬂicts!

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Easy Conﬂict Resolution $ git merge conflict_branch Auto-merged README CONFLICT (content): Merge conflict in README Automatic merge failed; fix conflicts and then commit the result. # fix conflict then commit $ vim README $ git add README $ git commit -m “fixed merge conflict”

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Collaboration with GIT

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Hosting a Git Repo • git-daemon • gitosis

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Hosting a Git Repo • git-daemon • gitosis

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github.com

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Fork your friends

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‘MySpace for hackers’

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Track forks of your repository

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Free for public repos

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• Still in beta • Email me at jnewland@gmail.com if you’d like an invite (20 left)

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Common Use Cases • Contributor • Create Patches • Send Patches • Maintainer • Review Patches • Apply Patches

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Contributor

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Fork, then clone • Fork repo at github http://github.com/jnewland/atlrug-demo/tree/master • Clone your copy of my repo $ git clone git@github.com/USERNAME/atlrug-demo.git

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Make changes $ git checkout -b my_branch $ echo “hello again” >> README $ git commit -a

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Track the upstream # add a remote $ git remote add jnewland git://github.com/ jnewland/atlrug-demo.git # add a branch $ git checkout -b jnewland/master # update the tracking branch $ git pull jnewland master

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Merge it all together # switch back to the master $ git checkout master # update master with your changes $ git merge my_branch # update master with upstream changes $ git merge jnewland/master

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Push it real good $ git push origin master

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Sending Patches • Old skool: $ git format-patch jnewland • New hotness - ‘Pull Request’

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No more emailing patches

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No more emailing patches

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Maintainer

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Receive pull request

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Grab mtodd’s changes # add a remote $ git remote add mtodd git://github.com/mtodd/ atlrug-demo.git # add a branch $ git checkout -b mtodd/master # pull the changes $ git pull mtodd master

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Merge, then push! # switch back to master $ git checkout master # merge $ git merge mtodd/master # push $ git push

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SVN Integration

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“the best part about GIT is that no one has to know you’re using it”

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basic git-svn workﬂow $ git svn clone REPO_URL # ... hack hack hack ... $ git commit -a # ... hack hack hack ... $ git commit -a $ git svn rebase $ git svn dcommit

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better workﬂow $ git svn clone REPO_URL $ git checkout -b new_branch # ... hack hack hack ... $ git commit -a $ git svn rebase $ git svn dcommit $ git checkout master $ git branch -d new_branch $ git svn rebase

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Pretty GUIs

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gitk • Bundled with git • Excellent visualization of branching history

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GitNub • http://github.com/Caged/ gitnub/tree/master • RubyCocoa

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More Resources • http://git.or.cz/ • http://cheat.errtheblog.com/s/git/ • http://github.com/guides • #git and #github on irc.freenode.org

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Questions? Comments? Flames?

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Jesse Newland jnewland@gmail.com http://jnewland.com

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flickr is awesome • http://flickr.com/photos/alper/528441936/ • http://flickr.com/photos/joan-fabregat/ 1947832858/ • http://flickr.com/photos/feria/2316579746/