deltas: Add _V0 to part #define

To make more explicitly clear that this is the version that matches
the version in the metadata.

src/libostree/ostree-repo-static-delta-private.h

@@ -30,14 +30,14 @@ G_BEGIN_DECLS
 #define OSTREE_STATIC_DELTA_OBJTYPE_CSUM_LEN 33
 
 /**
- * OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT:
+ * OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT_V0:
  *
  *   y  compression type (0: none, 'x': lzma)
  *   ---
  *   ay data source
  *   ay operations
  */
-#define OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT "(ayay)"
+#define OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT_V0 "(ayay)"
 
 /**
  * OSTREE_STATIC_DELTA_META_ENTRY_FORMAT:

src/libostree/ostree-repo-static-delta-processing.c

@@ -334,7 +334,7 @@ _ostree_static_delta_part_execute (OstreeRepo      *repo,
       goto out;
     }
         
-  payload = ot_variant_new_from_bytes (G_VARIANT_TYPE (OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT),
+  payload = ot_variant_new_from_bytes (G_VARIANT_TYPE (OSTREE_STATIC_DELTA_PART_PAYLOAD_FORMAT_V0),
                                        payload_data, FALSE);
   if (!_ostree_static_delta_part_execute_raw (repo, header, payload,
                                               cancellable, error))