code: func readInput(config config, filename *string) (input string, err error) {
  	if config.filenameIsCode {
  		input, err = *filename, nil
  		*filename = "<cmdline>"
  	} else if *filename == "-" {
  		var bytes []byte
  		bytes, err = ioutil.ReadAll(os.Stdin)
  		input = string(bytes)
  		*filename = "<stdin>"
  	} else {
  		var bytes []byte
  		bytes, err = ioutil.ReadFile(*filename)
  		input = string(bytes)
  	}
  	return
  }
docs: // readInput gets Jsonnet code from the given place (file, commandline, stdin).
  // It also updates the given filename to <stdin> or <cmdline> if it wasn't a real filename.