fix: parent verification on copy

errors/errors.go

@@ -16,4 +16,5 @@ var (
 	ErrInvalidAuthMethod    = errors.New("invalid auth method")
 	ErrPermissionDenied     = errors.New("permission denied")
 	ErrInvalidRequestParams = errors.New("invalid request params")
+	ErrSourceIsParent       = errors.New("source is parent")
 )