Re: VC / Git: amend function / mark for add / timing

[Alexandre Julliard <julliard@winehq.org>]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

> Currently VC's design is that it assesses the file's VC-status (mostly,
> whether or not it's under VC control and if so, under which backend and
> what is its current revision number and/or modification status) when the
> file gets opened, synchronously.
>
> This presumes that vc-registered is very quick.  If it is not, we have
> a problem.  In the case of Git, I believe there's no easy way for Emacs
> to figure out whether a file is under Git's control short of running
> Git, so the speed of vc-registered will depend on the speed of Git.

I believe that vc-git-registered is fast, but vc-git-state can be slow,
because git-diff-index unpacks the tree objects for all the files in the
head commit to check them against the index. On an unpacked repo with a
cold disk cache that can take a while.

I don't see a way to get a proper status without doing a diff-index, but
it would probably be possible to fix Git to apply the pathname filter at
a higher level to avoid accessing unnecessary objects.

-- 
Alexandre Julliard
julliard@winehq.org