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jnewland.com/tag/git
What is Git?
• A popular distributed version control system designed to handle very large projects with speed and efficiency.
• http://git.or.cz/
quick survey
• Who is not using source control?
• SVN?
• CVS? (still?)
• Written by Linus Torvalds
• Written to manage the Linux Kernel
Git History
Getting Git
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
For the weak
sudo port install git-core +svn
sudo apt-get install git-core
sudo yum install git-core
Initial Setup$ git config --global user.name='My Name'
$ git config --global [email protected]
# 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
Why Git?
• Distributed, not Centralized
• Revolutionizes how you use branching
• Extremely stupidly ridiculously fast, even with large projects
• Community
Centralizedvs
Distributed
Centralized VCS
• Repository
• History stored in central location
• Checkout
• A ‘working tree’
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.
Wait, commitshappen offline?
Commits happen offline!!!!!!!11!!!
on the plane
on the train
at that crappy coffee shop with the paid WiFi
at an ATLRUG meeting
Branching FTW
“But I don’t branch”
because you don’t use Git
quick survey #2
• How many of you use branching?
• Work exclusively on trunk/master?
• NEVER work on trunk/master?
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
Forget about ‘breaking the build’
• ‘Atomic’ commits are a thing of the past
• ‘Atomic’ merges
• Prototype well-developed changes
• Commit early and often
• Review and revise before you merge
Topic Branches
With Git, branches are now a part of my
everyday workflow
‘Tomorrow’ branch
‘Drunk’ branch
Performance
Offline Operations
• Performing a diff
• Viewing file history
• Committing changes
• Merging branches
• Obtaining any other revision of a file
• Switching branches
Online operationsare fast too
$ time svn co http://svn.rubyonrails.org/rails/trunk/
...
real 0m29.537s
Online operationsare fast too
$ time git clone --depth 1 git://github.com/josh/rails.git
...
real 0m9.088s
Online operationsare fast too
$ time git clone git://github.com/josh/rails.git
...
real 0m37.512s
Git for Subversion Users
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
Creating a Repo
$ pwd
~/src/foo
$ git init
$ git add .
$ git commit
Checking out a Repo
$ git clone REPO_URL
git status
• Untracked Files
• Brand new file
• Changed but not updated
• Locally changed file not in the index
• Changes to be committed
• ‘The Index’
The Index
• Staging area for your next commit
• Sort of like files marked A, M, D in svn status output
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.
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
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
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
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
Reverting Changes
$ git checkout PATH $ svn revert PATH
git revert != svn revert
# most similar to svn revert
$ git checkout .
# reverse commit <rev> and commit the result
$ git revert <rev>
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
More Branching# view available branches
$ git branch
* new_branch
master
# delete a branch
$ git branch -d ALREADY_MERGED_BRANCH
$ git branch -D BAD_BRANCH
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
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
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
Danger, Will Robinson
• Rebase is dangerous
• Rewrites commit history
• Don’t use on a branch you’re sharing
Oh noes! Merge Conflicts!
Easy Conflict Resolution
$ git merge conflict_branchAuto-merged READMECONFLICT (content): Merge conflict in READMEAutomatic merge failed; fix conflicts and then commit the result.
# fix conflict then commit
$ vim README
$ git add README
$ git commit -m “fixed merge conflict”
Collaboration with GIT
Hosting a Git Repo
• git-daemon
• gitosis
Hosting a Git Repo
• git-daemon
• gitosis
github.com
Fork your friends
‘MySpace for hackers’
Track forks of your repository
Free for public repos
• Still in beta
• Email me at [email protected] if you’d like an invite (20 left)
Common Use Cases
• Contributor
• Create Patches
• Send Patches
• Maintainer
• Review Patches
• Apply Patches
Contributor
Fork, then clone
• Fork repo at githubhttp://github.com/jnewland/atlrug-demo/tree/master
• Clone your copy of my repo$ git clone [email protected]/USERNAME/atlrug-demo.git
Make changes
$ git checkout -b my_branch
$ echo “hello again” >> README
$ git commit -a
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
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
Push it real good
$ git push origin master
Sending Patches
• Old skool:$ git format-patch jnewland
• New hotness - ‘Pull Request’
No more emailing patches
No more emailing patches
Maintainer
Receive pull request
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
Merge, then push!# switch back to master
$ git checkout master
# merge
$ git merge mtodd/master
# push
$ git push
SVN Integration
“the best part about GIT is that no one has to know you’re using it”
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
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
Pretty GUIs
gitk
• Bundled with git
• Excellent visualization of branching history
GitNub
• http://github.com/Caged/gitnub/tree/master
• RubyCocoa
More Resources
• http://git.or.cz/
• http://cheat.errtheblog.com/s/git/
• http://github.com/guides
• #git and #github on irc.freenode.org
Questions?Comments?
Flames?
Jesse [email protected]://jnewland.com
flickr is awesome
• http://flickr.com/photos/alper/528441936/
• http://flickr.com/photos/joan-fabregat/1947832858/
• http://flickr.com/photos/feria/2316579746/