hash: provide per-algorithm null OIDs
Up until recently, object IDs did not have an algorithm member, only a
hash. Consequently, it was possible to share one null (all-zeros)
object ID among all hash algorithms. Now that we're going to be
handling objects from multiple hash algorithms, it's important to make
sure that all object IDs have a correct algorithm field.
Introduce a per-algorithm null OID, and add it to struct hash_algo.
Introduce a wrapper function as well, and use it everywhere we used to
use the null_oid constant.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 119972e..3f29f8c 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1084,7 +1084,7 @@ static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
ref_transaction_add_update(
transaction, r->name,
REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
- &null_oid, &r->oid, NULL);
+ null_oid(), &r->oid, NULL);
if (ref_transaction_commit(transaction, &err))
goto cleanup;
