hash: require hash algorithm in oidread() and oidclr()

Both `oidread()` and `oidclr()` use `the_repository` to derive the hash
function that shall be used. Require callers to pass in the hash
algorithm to get rid of this implicit dependency.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule-config.c

@@ -682,7 +682,7 @@ static int gitmodule_oid_from_commit(const struct object_id *treeish_name,
 	int ret = 0;
 
 	if (is_null_oid(treeish_name)) {
-		oidclr(gitmodules_oid);
+		oidclr(gitmodules_oid, the_repository->hash_algo);
 		return 1;
 	}