We have this: only thing ever used is if it's 'view'. Do we need others?

$action = $request->getVal( 'action', 'view' );
if ( count( $request->getVal( 'diff' ) ) > 0 ) {
	$action = 'diff';
}

Just view: if ( Action::getActionName( $skin ) === 'view' )
Diff: if ($request()->getCheck( 'diff' ) )

BUT WHAT ARE WE EVEN DOING?!