\input texinfo @c -*- texinfo -*- @documentencoding UTF-8 @settitle Using Git to develop FFmpeg @titlepage @center @titlefont{Using Git to develop FFmpeg} @end titlepage @top @contents @chapter Introduction 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: @example git --help man git @end example shows you the available subcommands, @example git --help man git- @end example shows information about the subcommand . Additional information could be found on the @url{http://gitref.org, Git Reference} website. For more information about the Git project, visit the @url{http://git-scm.com/, Git website}. 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. @chapter Basics Usage @section Get Git You can get Git from @url{http://git-scm.com/} Most distribution and operating system provide a package for it. @section Cloning the source tree @example git clone git://source.ffmpeg.org/ffmpeg @end example This will put the FFmpeg sources into the directory @var{}. @example git clone git@@source.ffmpeg.org:ffmpeg @end example This will put the FFmpeg sources into the directory @var{} 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 @example git config --global core.autocrlf false @end example @anchor{Updating the source tree to the latest revision} @section Updating the source tree to the latest revision @example git pull (--rebase) @end example 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. @float IMPORTANT @command{--rebase} (see below) is recommended. @end float @section Rebasing your local branches @example git pull --rebase @end example 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. @section Adding/removing files/directories @example git add [-A] git rm [-r] @end example 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. @section Showing modifications @example git diff @end example will show all local modifications in your working directory as unified diff. @section Inspecting the changelog @example git log @end example You may also use the graphical tools like @command{gitview} or @command{gitk} or the web interface available at @url{http://source.ffmpeg.org/}. @section Checking source tree status @example git status @end example detects all the changes you made and lists what actions will be taken in case of a commit (additions, modifications, deletions, etc.). @section Committing @example git diff --check @end example 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 @example git diff -w -b @end example Also check the output of @example git status @end example to make sure you don't have untracked files or deletions. @example git add [-i|-p|-A] @end example Make sure you have told Git your name and email address @example git config --global user.name "My Name" git config --global user.email my@@email.invalid @end example Use @option{--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. @example git commit @end example 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 @example git config --global core.editor @end example or set by one of the following environment variables: @var{GIT_EDITOR}, @var{VISUAL} or @var{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 @command{git format-patch}. @section Preparing a patchset @example git format-patch [-o directory] @end example will generate a set of patches for each commit between @var{} and current @var{HEAD}. E.g. @example git format-patch origin/master @end example will generate patches for all commits on current branch which are not present in upstream. A useful shortcut is also @example git format-patch -n @end example which will generate patches from last @var{n} commits. By default the patches are created in the current directory. @section Sending patches for review @example git send-email @end example will send the patches created by @command{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. @var{git-email} package on Debian-based distros). @section Renaming/moving/copying files or contents of files Git automatically tracks such changes, making those normal commits. @example mv/cp path/file otherpath/otherfile git add [-A] . git commit @end example @chapter Git configuration In order to simplify a few workflows, it is advisable to configure both your personal Git installation and your local FFmpeg repository. @section Personal Git installation Add the following to your @file{~/.gitconfig} to help @command{git send-email} and @command{git format-patch} detect renames: @example [diff] renames = copy @end example @section Repository configuration In order to have @command{git send-email} automatically send patches to the ffmpeg-devel mailing list, add the following stanza to @file{/path/to/ffmpeg/repository/.git/config}: @example [sendemail] to = ffmpeg-devel@@ffmpeg.org @end example @chapter FFmpeg specific @section Reverting broken commits @example git reset @end example @command{git reset} will uncommit the changes till @var{} rewriting the current branch history. @example git commit --amend @end example allows one to amend the last commit details quickly. @example git rebase -i origin/master @end example will replay local commits over the main repository allowing to edit, merge or remove some of them in the process. @float NOTE @command{git reset}, @command{git commit --amend} and @command{git rebase} rewrite history, so you should use them ONLY on your local or topic branches. The main repository will reject those changes. @end float @example git revert @end example @command{git revert} will generate a revert commit. This will not make the faulty commit disappear from the history. @section Pushing changes to remote trees @example git push origin master --dry-run @end example Will simulate a push of the local master branch to the default remote (@var{origin}). And list which branches and ranges or commits would have been pushed. Git will prevent you from pushing changes if the local and remote trees are out of sync. Refer to @ref{Updating the source tree to the latest revision}. @example git remote add @end example 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. @example git push @end example Will push the changes to the @var{} repository. Omitting @var{} makes @command{git push} update all the remote branches matching the local ones. @section Finding a specific svn revision Since version 1.7.1 Git supports @samp{:/foo} syntax for specifying commits based on a regular expression. see man gitrevisions @example git show :/'as revision 23456' @end example will show the svn changeset @samp{r23456}. With older Git versions searching in the @command{git log} output is the easiest option (especially if a pager with search capabilities is used). This commit can be checked out with @example git checkout -b svn_23456 :/'as revision 23456' @end example or for Git < 1.7.1 with @example git checkout -b svn_23456 $SHA1 @end example where @var{$SHA1} is the commit hash from the @command{git log} output. @chapter Pre-push checklist 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 @option{--dry-run} first. And then inspecting the commits listed with @command{git log -p 1234567..987654}. The @command{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. @itemize @item @command{make distclean} @item @command{/path/to/ffmpeg/configure} @item @command{make fate} @item if fate fails due to missing samples run @command{make fate-rsync} and retry @end itemize 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. @chapter Server Issues Contact the project admins at @email{root@@ffmpeg.org} if you have technical problems with the Git server.