commit: add repository argument to lookup_commit

Add a repository argument to allow callers of lookup_commit to be more
specific about which repository to handle. This is a small mechanical
change; it doesn't change the implementation to handle repositories
other than the_repository yet.

As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/fetch-pack.c b/fetch-pack.c
index 771eb8a..9f3aa4a 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -498,7 +498,8 @@ static int find_common(struct fetch_pack_args *args,
 				case ACK_ready:
 				case ACK_continue: {
 					struct commit *commit =
-						lookup_commit(result_oid);
+						lookup_commit(the_repository,
+							      result_oid);
 					if (!commit)
 						die(_("invalid commit %s"), oid_to_hex(result_oid));
 					if (args->stateless_rpc
@@ -1278,7 +1279,7 @@ static int process_acks(struct packet_reader *reader, struct oidset *common)
 			if (!get_oid_hex(arg, &oid)) {
 				struct commit *commit;
 				oidset_insert(common, &oid);
-				commit = lookup_commit(&oid);
+				commit = lookup_commit(the_repository, &oid);
 				mark_common(commit, 0, 1);
 			}
 			continue;