/**
  * Returns the version of PHP_CodeCoverage.
  *
  * @return string
  */
 public static function id()
 {
     if (self::$version === NULL) {
         self::$version = self::VERSION;
         if (is_dir(dirname(dirname(__DIR__)) . '/.git')) {
             $dir = getcwd();
             chdir(__DIR__);
             $version = exec('git describe --tags');
             chdir($dir);
             if ($version) {
                 if (count(explode('.', self::VERSION)) == 3) {
                     self::$version = $version;
                 } else {
                     $version = explode('-', $version);
                     self::$version = self::VERSION . '-' . $version[2];
                 }
             }
         }
     }
     return self::$version;
 }