docs: function Watch_file(that,          // @arg this
                      watchFilePath, // @arg String   - watch file path
                      callback) {    // @arg Function - callback(null):void
      var timerID = 0;
  
      if (this._options.verbose) {
          console.log("  file: " + watchFilePath);
      }
  
      fs.watchFile(watchFilePath, _watchdogCallback);
  
      function _watchdogCallback() {
          if (timerID) {
              clearTimeout(timerID); timerID = 0;
          }
          timerID = setTimeout(function() {
              clearTimeout(timerID); timerID = 0;
  
              callback(null);
          }, that._options.delay);
      }
  }