packfile: convert has_sha1_pack to object_id

Convert this function to take a pointer to struct object_id and rename
it has_object_pack for consistency with has_object_file.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/packfile.h b/packfile.h
index a92c0b2..14ca34b 100644
--- a/packfile.h
+++ b/packfile.h
@@ -136,7 +136,7 @@ extern const struct packed_git *has_packed_and_bad(const unsigned char *sha1);
  */
 extern int find_pack_entry(struct repository *r, const unsigned char *sha1, struct pack_entry *e);
 
-extern int has_sha1_pack(const unsigned char *sha1);
+extern int has_object_pack(const struct object_id *oid);
 
 extern int has_pack_index(const unsigned char *sha1);