static function head($theme)
{
if ($theme->item()) {
$url = rss::item_feed($theme->item());
} else {
if ($theme->tag()) {
$url = rss::tag_feed($theme->tag());
}
}
if (!empty($url)) {
return "<link rel=\"alternate\" type=\"" . rest::RSS . "\" href=\"{$url}\" />";
}
}