deltas: Support including detached metadata in static deltas

This is very useful for the inline-parts case, as you can then include
detached signatures in a single file representing the commit.

It is not as important for the generic pull case, as the detached
metadata is only a single small file. Additionally the detached
metadata is not content referenced and may change after the static
delta file was created, so we need to pull the latest version anyway.

src/libostree/ostree-repo-pull.c

@@ -1532,7 +1532,19 @@ process_one_static_delta (OtPullData   *pull_data,
     
     if (!have_to_commit)
       {
-        FetchObjectData *fetch_data = g_new0 (FetchObjectData, 1);
+        FetchObjectData *fetch_data;
+        g_autofree char *detached_path = _ostree_get_relative_static_delta_path (from_revision, to_revision, "commitmeta");
+        g_autoptr(GVariant) detached_data = NULL;
+
+        detached_data = g_variant_lookup_value (metadata, detached_path, G_VARIANT_TYPE("a{sv}"));
+        if (detached_data && !ostree_repo_write_commit_detached_metadata (pull_data->repo,
+                                                                          to_revision,
+                                                                          detached_data,
+                                                                          cancellable,
+                                                                          error))
+          goto out;
+
+        fetch_data = g_new0 (FetchObjectData, 1);
         fetch_data->pull_data = pull_data;
         fetch_data->object = ostree_object_name_serialize (to_checksum, OSTREE_OBJECT_TYPE_COMMIT);
         fetch_data->is_detached_meta = FALSE;