Re: Arguments to git hooks

[Andrew Sayers <andrew-git@pileofstuff.org>]

On 06/05/12 19:35, jaseem abid wrote:
> Hello all,
> 
> I am trying to write a hook '.git/hooks/commit-msg' to be run before
> every commit.
> 
> How can I pass arguments to the script? Now by default the only arg I
> am getting is `.git/COMMIT_EDITMSG'`. I would love to get the list of
> files I tried to commit also into the script so that I can run a lint
> program on it before committing it. How can I get this done?

First, a standard warning - consider using a pre-receive hook instead of
a pre-commit hook.  A lot of git's power comes from making commits as
cheap as possible, so rules like "no committing until your code is
pretty" tend to stifle people.  For example, I often commit changes
before running lint-type operations, then use `git add -p` and `git
checkout -p` to selectively accept/reject individual changes.  When I'm
done, I `git commit --amend` to pretend the original commit never
happened.  A pre-receive hook gives you most of the same guarantees as a
pre-commit hook with almost none of the cost.

Having said that, there are situations where pre-commit hooks are a good
idea (like catching "DO NOT COMMIT" comments).  I've played with this a
little before, and never found a very satisfactory solution.  Here are
some important cases:

# git status will sometimes tell you the file that will be committed:
# edit foo
git add foo
git commit


# git status will sometimes need a bit of careful parsing:
# edit foo
# edit bar
git add foo
git commit


# git status sometimes tells you the right file but the wrong contents:
# edit foo
git add foo
# edit foo again
git commit


# but often git status will tell you the wrong file altogether:
# edit foo
# edit bar
git add foo
git commit bar


The best solution I've found is a `git commit` wrapper that does
something like `CHANGES="$(git commit $@ --dry-run -v)"` to get a
reliable diff, then starts work from there.

	- Andrew