Git and Vimdiff

Vimdiff screenshot

Vimdiff is my favourite diff tool. I've used many others, but I always come back to good old vimdiff. Git comes with git diff (man page: man git-diff) which shows the changes between various things Git knows about -- it's possible to show the changes between the working tree and the index, changes between two trees, and changes between two files.

More on git diff

The most commonly used form is simply git diff -- this shows the changes that are not currently staged for the next commit. If you've already staged changes, git diff --cached will show the difference between the index and the last commit.

Typing git diff branch will show a diff between the current working directory and the named branch.

I also use git diff --stat to see an overview of changes. A related command that I like to alias is git log --pretty=format:"[%h] %ae, %ar: %s" --stat which shows commit history with the files that were changed.

Vimdiff

Vimdiff can be run from the command-line with vimdiff file1 file2 [file3 [file4]]. This actually starts Vim in diff mode -- the previous command is actually equivalent to vim -d file1 file2 [file3 [file4]]. Vim requires a diff command to be available for this to work. Vim's documentation on this is available in :help diff.

Git Settings

Fortunately for us Vim fanatics, it's fairly easy to get Vimdiff working with Git. Git has a lot of options for working with diffs, and one is diff.tool (man page: man git-config). Also related is the merge.tool setting which can be set to allow Vimdiff to be used as the merge resolution program.

These settings can be passed to Git without changing any configuration files:

git difftool --tool=vimdiff --no-prompt

To tell Git to always use Vimdiff, issue the following commands:

git config --global diff.tool vimdiff
git config --global merge.tool vimdiff

Omit --global if you just want to set these for the repository in the working directory. Now typing git difftool should bring up Vimdiff.

Another useful option is difftool.prompt -- this will stop Vim prompting about launching vimdiff:

git config --global difftool.prompt false

If you're just trying these commands out, then the prompt will seem annoying, but there are cases where you might want to ignore a few files so it can be useful.

Editing Changed Files

I find myself combining Git's output with vim -p on certain occasions when I want to edit each changed file:

vim -p `git diff --name-only`

References and Links

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