Re: [PATCH] Add option to git-commit to allow empty log messages

[Jeff King <peff@peff.net>]

On Mon, Apr 05, 2010 at 12:58:22PM -0500, Jonathan Nieder wrote:

> > There's probably a lot of code out there doing `git commit -m"Yet
> > another revision"' from some cron job.
> 
> FWIW, I have no strong opinion about whether to add this --allow-empty-message
> option.  Maybe it would make something more convenient for someone,
> though that has to be weighed against it making it harder for everyone
> else to read the manual.

I meant to mention this in my other response: I would prefer if such an
option doesn't clutter up the usage message. --allow-empty is already
there, and probably doesn't need to be. "git commit -h 2>&1 | wc -l"
shows a whopping 39 lines, which IMHO is too many for a short usage
summary. I mean, "--no-post-rewrite", is that really one of the top-used
options?

> Hint:
> 
> 	parent=HEAD && : or whatever &&
> 	tree=$(git write-tree) &&
> 	printf "%s\n" message |
> 	commit=$(git commit-tree "$tree" -p "$parent") &&
> 	git update-ref refs/heads/somebranch "$commit"

In addition to the bug you mention later, you also probably want to do:

  parent=`git rev-parse --verify HEAD`
  [...]
  git update-ref \
    -m 'automated commit by tool X' \
    refs/heads/somebranch $commit $parent

which will give your reflog entry a more useful message, and will
protect against simultaneous updates losing history (update-ref will
make sure, while locked, that somebranch contains the $parent sha1 you
wrote as part of the commit object).

And of course it still doesn't handle parentless root commits.

So doing it right really is a bit more work than just calling "git
commit".

-Peff