Re: Getting diff in commit-msg hook?

Gerd Knops [off-list ref] writes:

When I commit certain files, I would like to send a diff via email to
interested parties.

So I added a commit-msg hook, which checks the list of files for that commit.
That part works fine. However in the email I would like to include a
diff of the file(s) in question.

Now when I run "git diff -- '$file'", I get no output, probably because the
file is in some semi-committed state.

So how can I obtain a diff for a file in a commit-msg hook?

How are you getting the list of files for the commit in that commit-msg
hook?  I think you are doing something like

	"git diff --cached --name-only"

The new state you are committing is in the index, and "the diff for the
commit" is "what is the difference between the state of the previous
commit and the state of this commit records", so

	" git diff --cached"

should give you what you want (and you do not need to do that per path.

Having said all that, I imagine you would realize that you do not want to
do this inside any of the hooks triggered by "git commit", as you learn to
work with git more.  I suspect you would probably find a hook triggered
when you push into another repository is more appropriate place for doing
this kind of thing.