Cache immutable command bridge metadata

parser.go

@@ -17,6 +17,13 @@ func (a *App) bridgeTree() *internalcobra.Command {
 	if a == nil {
 		return nil
 	}
+	if a.commandTree == nil {
+		a.commandTree = a.buildBridgeTree()
+	}
+	return a.commandTree
+}
+
+func (a *App) buildBridgeTree() *internalcobra.Command {
 	root := &internalcobra.Command{Name: a.identity.Name}
 	names := make([]string, 0, len(a.commands))
 	for name, node := range a.commands {