public function listNewVersions($plugin)
    {
        $code = is_string($plugin) ? $plugin : $this->pluginManager->getIdentifier($plugin);

        if (!$this->hasVersionFile($code)) {
            return [];
        }

        $databaseVersion = $this->getDatabaseVersion($code);
        return $this->getNewFileVersions($code, $databaseVersion);
    }