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>

resolve-undo.c

@@ -93,7 +93,8 @@ struct string_list *resolve_undo_read(const char *data, unsigned long size)
 				continue;
 			if (size < rawsz)
 				goto error;
-			oidread(&ui->oid[i], (const unsigned char *)data);
+			oidread(&ui->oid[i], (const unsigned char *)data,
+				the_repository->hash_algo);
 			size -= rawsz;
 			data += rawsz;
 		}