Re: [PATCH] builtin-commit: add --cached to operate only on index

> On the other hand, when we know we do not have to _show_ the list of
> staged/modified/untracked files (i.e. we already have the commit log
> message via -m, -F, or -C and we were told not to invoke editor), we do
> not have to call run_status(), only to discard its output.  In such a
> case, we are calling it only to see if we have something committable,
> and we should be able to optimize THAT without being told by the user
> with this new option.  Incidentally I just checked the scripted version;
> it does not do this optimization (git-commit.sh, ll. 514-517).  The C
> rewrite in 'next' does not have it in either (builtin-commit.c,
> ll. 387-390).  When no_edit is in effect, I think these two places can
> be replaced with an equivalent of "diff-index --cached HEAD --" (which
> should not hit the work tree at all) to see if there is anything to be
> committed.  For initial commit the check would obviously be "is the
> index empty?" instead.