object-file: handle compat objects in check_object_signature

Update check_object_signature to find the hash algorithm the exising
signature uses, and to use the same hash algorithm when recomputing it
to check the signature is valid.

This will be useful when teaching git ls-tree to display objects
encoded with the compat hash algorithm.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/object-file.c b/object-file.c
index b2d43d009898e8c1ff1fe3a353311189a9408d26..5fa4b14baee0ac7969c9ddde4f923c2b39a806f0 100644 (file)
--- a/object-file.c
+++ b/object-file.c
@@ -1094,9 +1094,11 @@ int check_object_signature(struct repository *r, const struct object_id *oid,
                           void *buf, unsigned long size,
                           enum object_type type)
 {
+       const struct git_hash_algo *algo =
+               oid->algo ? &hash_algos[oid->algo] : r->hash_algo;
        struct object_id real_oid;
 
-       hash_object_file(r->hash_algo, buf, size, type, &real_oid);
+       hash_object_file(algo, buf, size, type, &real_oid);
 
        return !oideq(oid, &real_oid) ? -1 : 0;
 }