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

[Junio C Hamano <gitster@pobox.com>]

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.