Revision as of 13:23, 22 September 2011

Git is a free and open source version control system. It is used by programmers to keep track of the different versions of the files composing a software.

Basic Git usage

If you are using Windows, please read the Git_Windows page.

Getting VLC or x264 source code via Git

$ git clone git://git.videolan.org/vlc.git

Voilà! The full VLC history should be on your hard disk in vlc/.

$ git clone git://git.videolan.org/x264.git

Voilà! The full x264 history should be on your hard disk in x264/.

If you want only the last 3 VLC revisions:

$ git clone git://git.videolan.org/vlc.git --depth 3

Clones without the full revision set (--depth) can't be used for backporting (or make sure to that you're including at least commits up to the common fork point).

You can also clone using http via our repo.or.cz mirror.

$ git clone http://repo.or.cz/r/vlc.git

See http://repo.or.cz/w/vlc.git (it's a mirror)

After cloning

$ git log

to see the full log of the trunk.

$ gitk

to see the log graphically.

You can also browse the sources via gitweb.

Configure your global git config

May need to use $ git repo-config {various options} 1.4.4.2 Requires the repo-config command rather than just config

Personal Information

Tell git your name. (use mostly by git-commit)

$ git config --global user.name "Your Name"
$ git config --global user.email "me@example.com"

Mail Information

To send patches you'll need a working mail / sendmail configuration. You can use msmtp to achieve this. Install it with tls and ssl activated and place the following config file (.msmtprc) in your home directory

# msmtp configuration file

# Set default values for all following accounts.
defaults
tls on
tls_starttls on
tls_trust_file /certificates/EquifaxSecureCertificateAuthority.crt
logfile /log/.msmtp.log

# GMAIL
account gmail
host smtp.gmail.com
port 587
protocol smtp
from user.name@gmail.com
auth on
user user.name@gmail.com

# Set a default account
account default : gmail

Then configure git to use msmtp. The password will be aske for upon sending mail.

$ git config --global sendemail.smtpserver /usr/local/bin/msmtp

The certificate for gmail can be found here: EquifaxSecureCertificateAuthority.crt

Using git with color (Tip)

If you want to use git with colored output use:

$ git config --global color.ui true

If you are using an old git version (prior to 1.5.5) and previous command didn't work, use:

$ git config --global color.diff auto
$ git config --global color.status auto
$ git config --global color.branch auto

Setting up "git up" (Tip)

If you want to be able to just keep in sync using "git up" use:

$ git config --global alias.up "pull --rebase"

And if you like your tree to be messy and don't want git to complain (like in svn) use:

$ git config --global alias.up '!sh -c "git commit -a -m "Before rebase" && git pull --rebase && git reset head^"'

Setting up "git wu" (Git What's Up) (Tip)

If you want to see what you are about to "git push":

$ git config --global alias.wu "log --stat origin..@{0}"

Now use:

$ git wu

Note that this only works for the master branch.

Setting up "git wup" (Git What's Up - with patch) (Tip)

If you want to see what you are about to "git push", along with the diff:

$ git config --global alias.wup "log -p origin..@{0}"

Now use:

$ git wup

General GIT Workflow

1. Make your file edits in your local repository.

2. "git commit" the changes in your local repository

3. "git pull --rebase" or "git up" (if you did git config --global alias.up "pull --rebase") to bring the rest of your local repository up to date

4. "git log origin..master" to check what you are going to commit

4. "git push" to move your changes up to the master

"git stash" if you want to "hide" your changes. Do this if you think there may be other commits against the same things you are working on and want to refresh your local checkout (using a git pull --rebase) from the master. Use "git stash apply" to get your stash back.

"git checkout -f master" if you think your tree is pretty hopeless, need a kill-and-fill to bring the master into your local repository.

List the local branch

You can now list your local branch by doing

$ git branch

which should ouput

$ git branch
* master

List your local non committed changes

$ git status | less

Commit

Now you can start to work on your tree. As soon as you feel you have reached a step in developement where you can commit your work locally, use

$ git commit -a

or

$ git commit <specific files>

If you wish to give credit to someone else's work (e.g. you are applying a third party patch):

$ git commit <specific files> --author "Name Surname <user@domain.com>"

List your commits

$ git log

Keeping your local working branch in sync

$ git pull --rebase

To shorten up that command type

$ git config --global alias.up "pull --rebase"

Now you can just type:

$ git up

Use a graphical interface

$ gitk          # Tree Browser
$ qgit          # Tree Browser
$ git-gui       # Commit/push/... editor

Submitting patches to the vlc-devel or x264-devel

First make sure you have read our Sending Patches page. And that you've read the Check List.

If you have been developing on vlc locally and (still) don't have write access, you can submit all your commits in one shot using:

$ rm -Rf patches
$ git format-patch -o patches origin
$ git send-email --to vlc-devel@videolan.org patches

If you want to create a cover letter for multiple patches use:

$ git format-patch -o patches origin -n --cover-letter
$ git send-email --annotate --cover-letter patches

If you have multiple patch consider using:

$ git send-email --compose --no-chain-reply-to --to vlc-devel@videolan.org patches

This will produce the patches for each local commit in the directory "patches" and send them. Use --no-chain-reply-to make sure it doesn't reply.

For x264, do the same with x264-devel@videolan.org

Don't do:

[PATCH 0/m]
- [PATCH 1/m]
  - [PATCH 2/m]
    - ...

But do:

[PATCH 0/m]
- [PATCH 1/m]
- [PATCH 2/m]
- ..

Advanced usage

Creating a secondary local branch

If you want to work on a specific project that could require a branch of the trunk, create a local branch of the current branch by doing:

$ git branch mywork

and to actually use it do:

$ git checkout mywork

Which could be summarized by:

$ git checkout -b mywork

Then do some commit on it... And you can go back to your original master branch by doing:

$ git checkout master

Fetching a remote branch

To see the remote branch use:

$ git branch -r

If the remote branch is named 0.8.6-bugfix

$ git branch 0.8.6-bugfix origin/0.8.6-bugfix 
Branch 0.8.6-bugfix set up to track remote branch refs/remotes/origin/0.8.6-bugfix.
$ git branch
 0.8.6-bugfix
 * master

To checkout that branch use:

$ git checkout 0.8.6-bugfix

To stay up-to-date a simple

$ git pull --rebase

Should be enough.

If warnings appear that files still need updating:

$ include/libvlc_internal.h: needs update
  include/mediacontrol_internal.h: needs update
  include/vlc/libvlc.h: needs update
  include/vlc_update.h: needs update
  modules/access/mms/mms.c: needs update
  ...

Then do a checkout -f to revert non committed local changes

$ git checkout -f

To stay up-to-date another

$ git pull --rebase

Should give no more warnings.

To push to the remote branch, use:

$git push origin 0.8.6-bugfix:0.8.6-bugfix

Creating a remote branch

If the new remote branch is named 0.9.0-bugfix, and is based on the local master branch. First make sure everything go as planned with the --dry-run option:

$ git push --dry-run origin master:refs/heads/0.9.0-stable
To git@git.videolan.org:vlc.git
* [new branch]      master -> 0.9.0-stable

Then push it:

$ git push origin master:refs/heads/0.9.0-stable
To git@git.videolan.org:vlc.git
* [new branch]      master -> 0.9.0-stable
$ git branch -r
 origin/0.9.0-stable
 origin/master

To checkout that branch now see Fetching a remote branch

Backporting commits

It is possible to "backport" commit between the master branch and a -bugfix branch. However since VDD'09, the bugfix branches have been splitted to their own git repositories. This leaves us with 2 cases.

Normal simple case

Go to your -bugfix branch:

$ git checkout 1.0-bugfix

Backport the commit:

$ git cherry-pick -x -s <sha-id of commit>

If git fails to do the backport by itself, you'll be presnted with the usual options in case of a failed merge or patching. Use "git status", your favorite editor or "git mergetool" to resolve the situation. Then use "git add" and "git commit -c <sha-id of backported commit>". Then push your commit as usual.

Case of VLC bugfix branches

Due to the number of commits in vlc.git and the amount of divergence between the master and 1.0-bugfix branches, they have been separated into two different git repositories. But that doesn't block you from backporting.

Get the -bugfix git:

$ git clone git://git.videolan.org/vlc/vlc-1.0.git vlc-bugfix

Add vlc.git as an additional remote:

$ git remote add vlc-master git://git.videolan.org/vlc.git

Update the information from vlc-master

$ git fetch vlc-master

Backport as normal

$ git cherry-pick -x -s <sha-id of commit>

Publishing your own fork

Goto http://repo.or.cz/w/vlc.git and click fork. You will be able to publish your work there.

Please don't forget to send a mail to the vlc-devel as soon as you create your fork.

Revert your non-committed local changes

$ git checkout -f

Edit or undo not yet pushed commits

This will undo the last commit

$ git reset HEAD^

which is the same as

$ git reset master^

(if your checked-out copy of your tree is master) And also the same as

$ git reset a44a594 # note that there is no need to use the full sha id

If you have a stack of patch that you have not yet committed you can delete one patch from the list using git rebase --interactive

$ git rebase --interactive origin
 pick eacf185 test
 pick 56322eb VLMA owner is vlma prod.

 # Rebase 826757e..56322eb onto 826757e
 #
 # Commands:
 #  pick = use commit
 #  edit = use commit, but stop for amending
 #  squash = use commit, but meld into previous commit

Diff-ing

You can diff between two branches using

$ git diff branch1 branch2

You can diff between the previous 10th commit and current using

$ git diff HEAD~10 HEAD

You can diff between the previous 10th commit and current of the branch "mywork" using

$ git diff mywork~10 mywork

Imagine that git log is like

$ git log
commit e0394f269305edd09843257e7c1d1a66aaf48ab3
Author: jb <jb>
Date:   Fri Apr 13 07:14:48 2007 +0000
   qt4 - Mousewheel (2)
commit e80b339081aa6755f67c9bd8e2aacf93a9a79d95
[..]
commit ff7004b70fd239e4120deb160e2991bd5237b8df
[..]
commit a44a594898f981a145cfcace5f16f8973f9eb46f
[..]
commit 690df705c963cf6bf6f5746d54bc97a85ff91919
[..]
commit 679f8b1c3e0baa469efa970588b95a625c595d64
[..]

$ git diff a44a594898f981a145cfcace5f16f8973f9eb46f~2 e80b339081aa6755f67c9bd8e2aacf93a9a79d95

Will be equivalent to:

$ git diff ff7004b70fd239e4120deb160e2991bd5237b8df e80b339081aa6755f67c9bd8e2aacf93a9a79d95

And to:

$ git diff HEAD~4 HEAD^

Remember that to produce a patch you should rather use git-format-patch than git-diff most of the time.

Patch-ing

You can apply patches using

$ git apply <patch>

Tracking regression

git has a great tool called git-bisect to help you to track a faulty commit. Imagine you are tracking a bug that is known to appear after 0.8.6 (assuming 0.8.6 is tagged):

$ git bisect start
$ git bisect bad # tell git current version has the bug you are tracking
$ git bisect good 0.8.6 # tell git 0.8.6 didn't have the bug

And then git will checkout a certain revision, and ask you to test it. And you simply say whether this version has the bug. If it has the bug:

$ git bisect bad

if the bug is not present:

$ git bisect good

And so on by bisection... At the end git will indicate the faulty commit. Most of the time this tool is really efficient to track regression.

If you can provide a script that test the presence of the bug

$ git bisect run <script_name>

will be able to track down the regression by itself. See git-bisect Documentation.

Using Git to push to VideoLAN git

Initial requirements

You must have credentials to push commits into the repository. For other contributors, please read upper Submitting patches to the vlc-devel or x264-devel paragraph.
Make sure you've set your name and email in your commits

$ git config --global user.name "Your Name"
$ git config --global user.email "me@example.com"

Convert your tree to use your ssh push commit access

$ vi vlc/.git/config

And replace

git://git.videolan.org/vlc.git

With

git@git.videolan.org:vlc.git

Staying up to date

 $ git pull --rebase

If you don't want to have to type --rebase everytime you pull do:

$ git config branch.master.rebase true

This one creates a merge object which is not how SVN worked, so let's use the first version...

 $ git pull

Pushing your work

 $ git log origin..master     # Check what you are going to push
 $ git push

Documentation about git

Difference between revisions of "Git"