Re: [PATCH] git-commit: add a prepare-commit-msg hook

[Paolo Bonzini <bonzini@gnu.org>]

> I think that the approach has one huge advantage.  Commands
> other than "git commit" itself ("git merge", "git rebase", "git
> am", etc.) do call "git commit" to record the changes they made.
> I suspect these command would not want this template behaviour,
> and not adding this custom commit message "feature" to "git
> commit" would avoid the risk of breaking them.

My patch does not do that.  Of all these commands, only git-rebase uses 
porcelain git-commit rather than plumbing git-commit-tree, and it uses 
the -C or -F options (which disable the hook in my patch).

> At the same time, this exact issue could be a drawback.  Some of
> them _might_ want it.  But in that case, the the custom template
> "hook" needs to be told _why_ it is being called, so that it can
> adjust its behaviour.

I would like to understand why both of you have not considered the point 
  that the script would need the updated index from git-commit.  Because 
short of reusing half of the old Bourne-shell git-commit, I don't see 
how this would be possible, but maybe there's something obvious.  Or 
maybe we need new plumbing like git-build-index -- then I'd still need 
to complicate my script to build a template commit message, but I 
wouldn't need to muddle myself (not too much at least) in handling the 
command line.

Paolo