ffmpeg / doc / git-howto.txt

About Git write access:

Before everything else, you should know how to use GIT properly.
Luckily Git comes with excellent documentation.

  git --help
  man git

shows you the available subcommands,

  git <command> --help
  man git-<command>

shows information about the subcommand <command>.

The most comprehensive manual is the website Git Reference

For more information about the Git project, visit

Consult these resources whenever you have problems, they are quite exhaustive.

You do not need a special username or password.
All you need is to provide a ssh public key to the Git server admin.

What follows now is a basic introduction to Git and some FFmpeg-specific
guidelines. Read it at least once, if you are granted commit privileges to the
FFmpeg project you are expected to be familiar with these rules.


0. Get GIT:

  Most distributions have a git package, if not
  You can get git from

1. Cloning the source tree:

    git clone git:// <target>

  This will put the FFmpeg sources into the directory <target>.

    git clone <target>

  This will put the FFmpeg sources into the directory <target> and let
  you push back your changes to the remote repository.

2. Updating the source tree to the latest revision:

    git pull (--ff-only)

  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.
  Caveat: Since merge commits are forbidden at least for the initial
          months of git --ff-only or --rebase (see below) are recommended.
          --ff-only will fail and not create merge commits if your branch
          has diverged (has a different history) from the tracked branch.

2.a Rebasing your local branches:

    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.

3. Adding/removing files/directories:

    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.

4. Showing modifications:

    git diff <filename(s)>

  will show all local modifications in your working directory as unified diff.

5. Inspecting the changelog:

    git log <filename(s)>

  You may also use the graphical tools like gitview or gitk or the web
  interface available at

6. Checking source tree status:

    git status

  detects all the changes you made and lists what actions will be taken in case
  of a commit (additions, modifications, deletions, etc.).

7. Committing:

    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

    git status

  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, e.g. by running
    git config --global "My Name"
    git config --global my@email.invalid
  (--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 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 core.editor

  or set by one of the following environment variables:

  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.

8. Renaming/moving/copying files or contents of files:

  Git automatically tracks such changes, making those normal commits.

    mv/cp path/file otherpath/otherfile

    git add [-A] .

    git commit

  Do not move, rename or copy files of which you are not the maintainer without
  discussing it on the mailing list first!

9. Reverting broken commits

    git revert <commit>

  git revert will generate a revert commit. This will not make the faulty
  commit disappear from the history.

    git reset <commit>

  git reset will uncommit the changes till <commit> rewriting the current
  branch history.

    git commit --amend

  allows 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.

  Note that the reset, commit --amend and rebase rewrite history, so you
  should use them ONLY on your local or topic branches.

  The main repository will reject those changes.

10. Preparing a patchset.

    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.

11. Sending patches for review

    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).

12. Pushing changes to remote trees

    git push

  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 2 and 2.a 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.

13. Finding a specific svn revision

  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
  the 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 SHA1 from the 'git log' output.

Contact the project admins <root at ffmpeg dot org> if you have technical
problems with the GIT server.