get_sha1(): fix error status regression

In finish_object_disambiguation(), if the candidate hasn't been
checked, there are two cases:

 - It is the first and only object that match the prefix; or
 - It replaced another object that matched the prefix but that
   object did not satisfy ds->fn() callback.

And the former case we set ds->candidate_ok to true without doing
anything else, while for the latter we check the candidate, which
may set ds->candidate_ok to false.

At this point in the code, ds->candidate_ok can be false only if
this last-round check found that the candidate does not pass the
check, because the state after update_candidates() returns cannot
satisfy

    !ds->ambiguous && ds->candidate_exists && ds->candidate_checked

and !ds->canidate_ok at the same time.

Hence, when we execute this "return", we know we have seen more than
one object that match the prefix (and none of them satisfied ds->fn),
meaning that we should say "the short name is ambiguous", not "there
is no object that matches the prefix".

Noticed by Jeff King.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/sha1_name.c b/sha1_name.c
index 2e2dbb866431eb6f604559daae2d5cdc4cb38d04..c824bdd3eb5ba146b21e7c0046ec1414fa9a2971 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -212,7 +212,7 @@ static int finish_object_disambiguation(struct disambiguate_state *ds,
                                    ds->fn(ds->candidate, ds->cb_data));
 
        if (!ds->candidate_ok)
-               return SHORT_NAME_NOT_FOUND;
+               return SHORT_NAME_AMBIGUOUS;
 
        hashcpy(sha1, ds->candidate);
        return 0;