docs: function _shouldKeepExisting(file, text)
  {
  return Promise.coroutine(function *() {
  	if (!(yield fs.fileExists(file)))
  		return false;
  
  //	var st = yield fs.stat(file);
  //	if (st > _ThisBuild)
  //		l.logw("File is used multiple times: '" + file)+"'");
  
  	// read the existing file and compare with new contents. ignore if nothing changed
  	try
  	{
  		var existingText = yield fs.readFile(file, "utf8");
  		if (existingText == text)
  		{
  			//l.vlog("Skipping (unchanged): '" + file + "'");
  			return true;
  		}
  	}
  	catch (e)
  	{
  		l.logw("Failed to compare existing file " + path.basename(file) + " (will try and overwrite): " + _.niceStackTrace(e));
  		// and continue below...
  	}
  	return false;
  })();
  }