Re: [PATCH] cache-tree: populate cache-tree on successful merge

[David Turner <dturner@twopensource.com>]

On Tue, 2015-07-28 at 13:04 -0700, Junio C Hamano wrote:
> Junio C Hamano <gitster@pobox.com> writes:
> 
> > David Turner <dturner@twopensource.com> writes:
> >
> >> The work done to produce the cache-tree is work that the commit would
> >> otherwise have to do.  So we're spending extra time in one place to
> >> eliminate that work in a different place.
> >
> > Good point.  Thanks.
> 
> Hmm, I forgot about another codepath.  What about operations that
> are purely done to pouplate the index, without necessarily creating
> a tree out of the index?
> 
> The most worrisome is "git checkout $branch" (two-tree merge).

Git checkout $branch already populates the cache-tree; this is due to
patches I added last year:

commit aecf567cbfb6ab46e82f7f5df36fb6a2dd5bee69
Author: David Turner <dturner@twopensource.com>
Date:   Sat Jul 5 21:06:56 2014 -0700

    cache-tree: create/update cache-tree on checkout
    
    When git checkout checks out a branch, create or update the
    cache-tree so that subsequent operations are faster.
----

Admittedly, we do not test for the case where we must do a two-way merge
during a checkout, but I just tested that case, and it appears that we
do already populate the cache-tree in that case.