public function flagArchive(\SplFileInfo $archive, $flag)
{
// delete all old flags
$this->unflagArchive($archive);
// flag the passed archive
file_put_contents($archive->getPathname() . $flag, $archive->getPathname());
// set correct user/group for the flag file
$this->setUserRight(new \SplFileInfo($archive->getPathname() . $flag));
}