Basic Git usage

Fundamentals

Basic operations

Initial checkout:

git-clone git://git.mplayerhq.hu/ffmpeg ffmpeg-git

And if you want libswscale as well:

cd ffmpeg-git
git-clone git://git.mplayerhq.hu/libswscale

Update (this has to be done in ffmpeg-git and in its libswscale subdir as they are currently separate repositories):

git-pull

Make some changes, decide they're bad, revert the changes:

git-reset --soft <commit>

Make some changes, commit them, decide to revert the commit:

git-revert <commit>

Make a branch:

git-branch <name of branch>

Switch to a branch (make it the active branch such that source files reflect the source in that branch):

git-checkout <name of branch>

Delete a branch (must be merged with HEAD of current branch, keeping the history):

git-branch -d <name of branch>

Delete a branch (irrespective of merge status, removing the history):

git-branch -D <name of branch>

To "fix" the last commit/commit message:

git-commit --amend

Specifying revisions

The syntax for specifying particular commits from branches in git is a little complex but is covered in the 'SPECIFYING REVISIONS' section of the git-rev-parse man page. git-rev-parse html man page

Guis and helper scripts

Main article: Git Guis

Also see git-*.sh at http://www1.mplayerhq.hu/~reimar/

Working on a series of incremental, dependent patches

Edit some files making functional changes. Commit changes locally - prompted for a commit message using $EDITOR to write it

git-commit -a

Edit some files making cosmetic changes and commit again.

git-commit -a

Prepare patches for e-mail submission (this creates the patches numbered and in order for easy submission):

git-format-patch <commit>

Generate a diff of branch 2 against branch 1 (i.e. branch 1 + patch = branch 2)

git-diff <name of branch 1> <name of branch 2>

Apply and commit a git-diff style patch in a working Git tree:

git-am foo.patch

Apply a git-diff style patch in any working directory containing the correct source files to be patched:

git-apply foo.patch

(Note: git-am will create a new commit using the extra metadata for the commit message, etc. whereas git-apply just patches the files)

When submitting a set of patches to be applied in order, it is common to want to go back and edit one of the intermediate commits depending on feedback for the patches. This process can be easily achieved using the marvellous git-rebase:

git-rebase -i <commit preceding the ones in which interested>

(Note: When using git-rebase, it uses the $EDITOR environment variable so make sure it's set to your text editor of choice.)

This will display a list of the commits from the one after that specified and HEAD and gives you the opportunity to remove commits, reorder them, edit them and 'squash' a commit into the one preceding it. When you've edited this list accordingly you should be presented with those commits that were requested to be edited, or need editing, in order. Cool, huh? :)

Get a hack out of the way

You probably need a fairly new version of git for this feature.

To quickly get rid of some local, non-committed changes:

git-stash

To get them back again:

git-stash apply