Re: update-index --assume-unchanged doesn't make things go fast

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 28, 2008, 02:03 UTC
Message-ID: <7vd4m2l3i2.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <m3lk0qiy2i.fsf@localhost.localdomain>

Jakub Narebski <jnareb@gmail.com> writes:

> By the way, from time to time there on this mailing list is idea
> to add entries for directories in the index.  This could help situation
> like yours, tracking emty directories, faster operations when some trees
> are unchanged, subtree <-> subproject changes.

Tracking empty directories might be helped by having an explicit entry in the index (even though it may not be the only possible implementation). I however suspect you are overvaluing it for "some trees are unchanged" case:

        $ mkdir -p a/b
        $ stat a | grep Modify
        Modify: 2008-06-27 11:38:13.000000000 -0700
        $ >a/b/c
        $ stat a | grep Modify
        Modify: 2008-06-27 11:38:13.000000000 -0700
        $ >a/d
        $ stat a | grep Modify
        Modify: 2008-06-27 11:38:32.000000000 -0700

You have to descend into the leaf level anyway and directory mtime does not allow you to check that much.