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

[Derrick Stolee <stolee@gmail.com>]

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.

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

Thanks,
-Stolee


diff --git a/sha1_name.c b/sha1_name.c
index 49ba67955..9f8a33e82 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -153,7 +153,9 @@ static void unique_in_pack(struct packed_git *p,
         uint32_t num, last, i, first = 0;
         const struct object_id *current = NULL;

-       open_pack_index(p);
+       if (open_pack_index(p) || !p->num_objects)
+               return;
+
         num = p->num_objects;
         last = num;
         while (first < last) {
@@ -513,7 +515,9 @@ static void find_abbrev_len_for_pack(struct 
packed_git *p,
         uint32_t num, last, first = 0;
         struct object_id oid;

-       open_pack_index(p);
+       if (open_pack_index(p) || !p->num_objects)
+               return;
+
         num = p->num_objects;
         last = num;
         while (first < last) {