code: public function addnew(HTTPRequest $r)
      {
          return Controller::curr()->redirect(Controller::join_links($this->owner->gridField->Link("item"), "new"));
      }
docs: Redirecting to the current URL doesn't do anything, so this is just a dummy action
  that gives the request somewhere to go in order to force a reload, and then just
  redirects back to the original link.
  
  @param HTTPRequest The request object