Re: [PATCH v4 4/4] sha1_name: minimize OID comparisons during disambiguation

[Jeff King <peff@peff.net>]

On Tue, Oct 10, 2017 at 09:11:15AM -0400, Derrick Stolee wrote:

> On 10/10/2017 8:56 AM, Junio C Hamano wrote:
> > Jeff King <peff@peff.net> writes:
> > 
> > > OK, I think that makes more sense. But note the p->num_objects thing I
> > > mentioned. If I do:
> > > 
> > >    git pack-objects .git/objects/pack/pack </dev/null
> > > 
> > > then I have a pack with zero objects, which I think we'd similarly want
> > > to return early from. I.e., I think we need:
> > > 
> > >    if (p->num_objects)
> > > 	return;
> > > 
> > > Technically that also covers open_pack_index() failure, too, but that's
> > > a subtlety I don't think we should rely on.
> > True.  I notice that the early part of the two functions look almost
> > identical.  Do we need error condition handling for the other one,
> > too?
> 
> I prefer to fix the problem in all code clones when they cause review
> friction, so I'll send a fifth commit showing just the diff for these
> packfile issues in sha1_name.c. See patch below.

Ah, that answers my earlier question. Junio mean unique_in_pack(). And
yeah, I think it suffers from the same problem.

> Should open_pack_index() return a non-zero status if the packfile is empty?
> Or, is there a meaningful reason to have empty packfiles?

I can't think of a compelling reason to have an empty packfile. But nor
do I think we should consider them an error when we can handle them
quietly (and returning non-zero status would cause Git to complain on
many operations in a repository that has such a file).

-Peff