protected function checkCanExecute(User $user)
{
parent::checkCanExecute($user);
$oldimage = $this->getRequest()->getText('oldimage');
if (strlen($oldimage) < 16 || strpos($oldimage, '/') !== false || strpos($oldimage, '\\') !== false) {
throw new ErrorPageError('internalerror', 'unexpected', array('oldimage', $oldimage));
}
$this->oldFile = RepoGroup::singleton()->getLocalRepo()->newFromArchiveName($this->getTitle(), $oldimage);
if (!$this->oldFile->exists()) {
throw new ErrorPageError('', 'filerevert-badversion');
}
}
