refactor label anno manager

Author: ColdsteelRail

xset/revisionowner/revision_owner.go

@@ -52,6 +52,7 @@ func (r *revisionOwner) GetGroupVersionKind() schema.GroupVersionKind {
 func (r *revisionOwner) GetMatchLabels(parent metav1.Object) map[string]string {
 	obj := parent.(v1alpha1.XSetObject)
 	xsetSpec := r.XSetController.GetXSetSpec(obj)
+	// that's ok to return nil, manager will use nothingSelector instead
 	return xsetSpec.Selector.MatchLabels
 }