builtin: use default hash when outside a repository

We have some commands that can operate inside or outside a repository.
If we're operating outside a repository, we clearly cannot use the
repository's hash algorithm as a default since it doesn't exist, so
instead, let's pick the default instead of specifically SHA-1.  Right
now this results in no functional change since the default is SHA-1, but
that may change in the future.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/patch-id.c

@@ -254,7 +254,7 @@ int cmd_patch_id(int argc,
 	 * the code that computes patch IDs to always use SHA1.
 	 */
 	if (!the_hash_algo)
-		repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
+		repo_set_hash_algo(the_repository, GIT_HASH_DEFAULT);
 
 	generate_id_list(opts ? opts > 1 : config.stable,
 			 opts ? opts == 3 : config.verbatim);