Using git to develop FFmpeg
Table of Contents
- 1. Introduction
- 2. Basics Usage
- 2.1 Get GIT
- 2.2 Cloning the source tree
- 2.3 Updating the source tree to the latest revision
- 2.4 Rebasing your local branches
- 2.5 Adding/removing files/directories
- 2.6 Showing modifications
- 2.7 Inspecting the changelog
- 2.8 Checking source tree status
- 2.9 Committing
- 2.10 Preparing a patchset
- 2.11 Sending patches for review
- 2.12 Renaming/moving/copying files or contents of files
- 3. Git configuration
- 4. FFmpeg specific
- 5. pre-push checklist
- 6. Server Issues
This document aims in giving some quick references on a set of useful git commands. You should always use the extensive and detailed documentation provided directly by git:
git --help man git
shows you the available subcommands,
git <command> --help man git-<command>
shows information about the subcommand <command>.
Additional information could be found on the Git Reference website
For more information about the Git project, visit the
Consult these resources whenever you have problems, they are quite exhaustive.
What follows now is a basic introduction to Git and some FFmpeg-specific guidelines to ease the contribution to the project
You can get git from http://git-scm.com/ Most distribution and operating system provide a package for it.
git clone git://source.ffmpeg.org/ffmpeg <target>
This will put the FFmpeg sources into the directory <target>.
git clone firstname.lastname@example.org:ffmpeg <target>
This will put the FFmpeg sources into the directory <target> and let you push back your changes to the remote repository.
Make sure that you do not have Windows line endings in your checkouts, otherwise you may experience spurious compilation failures. One way to achieve this is to run
git config --global core.autocrlf false
git pull (--rebase)
pulls in the latest changes from the tracked branch. The tracked branch can be remote. By default the master branch tracks the branch master in the remote origin.
--rebase (see below) is recommended.
git pull --rebase
fetches the changes from the main repository and replays your local commits over it. This is required to keep all your local changes at the top of FFmpeg’s master tree. The master tree will reject pushes with merge commits.
git add [-A] <filename/dirname> git rm [-r] <filename/dirname>
GIT needs to get notified of all changes you make to your working directory that makes files appear or disappear. Line moves across files are automatically tracked.
git diff <filename(s)>
will show all local modifications in your working directory as unified diff.
git log <filename(s)>
You may also use the graphical tools like gitview or gitk or the web interface available at http://source.ffmpeg.org/
detects all the changes you made and lists what actions will be taken in case of a commit (additions, modifications, deletions, etc.).
git diff --check
to double check your changes before committing them to avoid trouble later on. All experienced developers do this on each and every commit, no matter how small. Every one of them has been saved from looking like a fool by this many times. It’s very easy for stray debug output or cosmetic modifications to slip in, please avoid problems through this extra level of scrutiny.
For cosmetics-only commits you should get (almost) empty output from
git diff -w -b <filename(s)>
Also check the output of
to make sure you don’t have untracked files or deletions.
git add [-i|-p|-A] <filenames/dirnames>
Make sure you have told git your name and email address
git config --global user.name "My Name" git config --global user.email email@example.com
Use –global to set the global configuration for all your git checkouts.
Git will select the changes to the files for commit. Optionally you can use the interactive or the patch mode to select hunk by hunk what should be added to the commit.
Git will commit the selected changes to your current local branch.
You will be prompted for a log message in an editor, which is either set in your personal configuration file through
git config --global core.editor
or set by one of the following environment variables: GIT_EDITOR, VISUAL or EDITOR.
Log messages should be concise but descriptive. Explain why you made a change, what you did will be obvious from the changes themselves most of the time. Saying just "bug fix" or "10l" is bad. Remember that people of varying skill levels look at and educate themselves while reading through your code. Don’t include filenames in log messages, Git provides that information.
Possibly make the commit message have a terse, descriptive first line, an empty line and then a full description. The first line will be used to name the patch by git format-patch.
git format-patch <commit> [-o directory]
will generate a set of patches for each commit between <commit> and current HEAD. E.g.
git format-patch origin/master
will generate patches for all commits on current branch which are not present in upstream. A useful shortcut is also
git format-patch -n
which will generate patches from last n commits. By default the patches are created in the current directory.
git send-email <commit list|directory>
will send the patches created by
git format-patch or directly
generates them. All the email fields can be configured in the global/local
configuration or overridden by command line.
Note that this tool must often be installed separately (e.g. git-email
package on Debian-based distros).
Git automatically tracks such changes, making those normal commits.
mv/cp path/file otherpath/otherfile git add [-A] . git commit
In order to simplify a few workflows, it is advisable to configure both your personal Git installation and your local FFmpeg repository.
Add the following to your ‘~/.gitconfig’ to help
git format-patch detect renames:
[diff] renames = copy
In order to have
git send-email automatically send patches
to the ffmpeg-devel mailing list, add the following stanza
[sendemail] to = firstname.lastname@example.org
git reset <commit>
git reset will uncommit the changes till <commit> rewriting
the current branch history.
git commit --amend
allows one to amend the last commit details quickly.
git rebase -i origin/master
will replay local commits over the main repository allowing to edit, merge or remove some of them in the process.
git commit --amend and
rewrite history, so you should use them ONLY on your local or topic branches.
The main repository will reject those changes.
git revert <commit>
git revert will generate a revert commit. This will not make the
faulty commit disappear from the history.
Will push the changes to the default remote (origin). Git will prevent you from pushing changes if the local and remote trees are out of sync. Refer to and to sync the local tree.
git remote add <name> <url>
Will add additional remote with a name reference, it is useful if you want to push your local branch for review on a remote host.
git push <remote> <refspec>
Will push the changes to the <remote> repository.
Omitting <refspec> makes
git push update all the remote
branches matching the local ones.
Since version 1.7.1 git supports :/foo syntax for specifying commits based on a regular expression. see man gitrevisions
git show :/'as revision 23456'
will show the svn changeset r23456. With older git versions searching in
git log output is the easiest option (especially if a pager with
search capabilities is used).
This commit can be checked out with
git checkout -b svn_23456 :/'as revision 23456'
or for git < 1.7.1 with
git checkout -b svn_23456 $SHA1
where $SHA1 is the commit hash from the
git log output.
Once you have a set of commits that you feel are ready for pushing, work through the following checklist to doublecheck everything is in proper order. This list tries to be exhaustive. In case you are just pushing a typo in a comment, some of the steps may be unnecessary. Apply your common sense, but if in doubt, err on the side of caution.
First, make sure that the commits and branches you are going to push
match what you want pushed and that nothing is missing, extraneous or
wrong. You can see what will be pushed by running the git push command
with –dry-run first. And then inspecting the commits listed with
git log -p 1234567..987654. The
git status command
may help in finding local changes that have been forgotten to be added.
Next let the code pass through a full run of our testsuite.
- if fate fails due to missing samples run
make fate-rsyncand retry
Make sure all your changes have been checked before pushing them, the testsuite only checks against regressions and that only to some extend. It does obviously not check newly added features/code to be working unless you have added a test for that (which is recommended).
Also note that every single commit should pass the test suite, not just the result of a series of patches.
Once everything passed, push the changes to your public ffmpeg clone and post a merge request to ffmpeg-devel. You can also push them directly but this is not recommended.
Contact the project admins email@example.com if you have technical problems with the GIT server.