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>

builtin/rm.c

@@ -377,7 +377,7 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 	if (!force) {
 		struct object_id oid;
 		if (repo_get_oid(the_repository, "HEAD", &oid))
-			oidclr(&oid);
+			oidclr(&oid, the_repository->hash_algo);
 		if (check_local_mod(&oid, index_only))
 			exit(1);
 	}