icingaweb2/modules/monitoring/application/views/scripts/show/components/hostgroups.phtml

<?php

if (empty($object->hostgroups)) return;

$list = array();
foreach ($object->hostgroups as $name => $alias) {
    $list[] = $this->qlink($alias, 'monitoring/list/hosts', array(
        'hostgroup' => $name
    ));
}
printf(
    "<tr><th>%s</th><td>%s %s</td></tr>\n",
    $this->translate('Hostgroups'),
    $this->icon('host'),
    implode(', ', $list)
);