* @param string|null $timestamp Value of wl_notificationtimestamp from the DB
* @param UserIdentity $user
* @param LinkTarget $target
- * @return string TS_MW timestamp or null
+ * @return string|null TS_MW timestamp or null if all revision were seen
*/
public function getLatestNotificationTimestamp(
$timestamp, UserIdentity $user, LinkTarget $target );