// Try cache
if ( !$this->mRefreshCache ) {
    $difftext = $cache->get( $key );
    if ( $difftext ) {
        wfIncrStats( 'diff_cache.hit' );
        $difftext = $this->localiseDiff( $difftext );
        $difftext .= "\n<!-- diff cache key $key -->\n";

        return $difftext;
    }
} // don't try to load but save the result