src/Extensions/GridFieldBetterButtonsItemRequest.php
public function addnew(HTTPRequest $r)
    {
        return Controller::curr()->redirect(Controller::join_links($this->owner->gridField->Link("item"), "new"));
    }
public function addnew(HTTPRequest $r)
    {
        return Controller::curr()->redirect(Controller::join_links($this->owner->gridField->Link("item"), "new"));
    }
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