public function execute(Git_Hook_PushDetails $push_details, $commit_sha1)
 {
     $rev_id = $push_details->getRepository()->getFullName() . '/' . $commit_sha1;
     $text = $this->git_exec->catFile($commit_sha1);
     $GLOBALS['group_id'] = $push_details->getRepository()->getProject()->getId();
     $this->reference_manager->extractCrossRef($text, $rev_id, Git::REFERENCE_NATURE, $push_details->getRepository()->getProject()->getId(), $push_details->getUser()->getId());
 }