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 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

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 jnewland@gmail.com 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 git@github.com/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 Newlandjnewland@gmail.comhttp://jnewland.com

flickr is awesome

• http://flickr.com/photos/alper/528441936/

• http://flickr.com/photos/joan-fabregat/1947832858/

• http://flickr.com/photos/feria/2316579746/