public function assertCommitMessageIsValid(Project $project, $commit_message)
 {
     if ($project->isSVNMandatoryRef()) {
         // Marvelous, extractCrossRef depends on globals group_id to find the group
         // when it's not explicit... yeah!
         $GLOBALS['group_id'] = $project->getID();
         if (!$this->reference_manager->stringContainsReferences($commit_message, $project)) {
             throw new Exception('Commit message must contains a reference');
         }
     }
 }