code: public RedwoodConfiguration file(String file){
      LogRecordHandler visibility = new VisibilityHandler();
      LogRecordHandler console = new Redwood.FileHandler(file);
      return this
          .rootHandler(visibility)
          .handler(visibility, console);
    }
docs: Add a file pipeline to the Redwood handler tree.
  That is, print log messages to a given file.
  Calling this multiple times will result in messages being printed
  to multiple files (or, multiple times to the same file).
  @param file The path of the file to log to. This path is not checked
  for correctness here.
  @return this