patch-id: use stable patch-id for rebases

Git doesn't persist patch-ids during the rebase process, so there is
no need to specifically invoke the unstable variant. Use the stable
logic for all internal patch-id calculations to minimize the number of
code paths and improve test coverage.

Signed-off-by: Jerry Zhang <jerry@skydio.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/patch-ids.h b/patch-ids.h
index ab6c6a6..490d739 100644
--- a/patch-ids.h
+++ b/patch-ids.h
@@ -20,7 +20,7 @@ struct patch_ids {
 };
 
 int commit_patch_id(struct commit *commit, struct diff_options *options,
-		    struct object_id *oid, int, int);
+		    struct object_id *oid, int);
 int init_patch_ids(struct repository *, struct patch_ids *);
 int free_patch_ids(struct patch_ids *);