param memento gef memento tigri gef undo undo manag add memento tigri gef undo memento overrid add memento memento memento todo shouldn referenc current project instead appropri undo manag retriev correct project project project manag manag current project argouml kernel undo manag undo undo manag undo start chain todo gef need pass descript undo start interact diagram interact todo presum fix issu gef need adapt memento select memento undo add command diagram command memento start chain 