code: func withCmdCommentString(comment string, platform string) runConfigModifier {
  	return func(runConfig *container.Config) {
  		runConfig.Cmd = append(getShell(runConfig, platform), "#(nop) "+comment)
  	}
  }
docs: // withCmdCommentString exists to maintain compatibility with older versions.
  // A few instructions (workdir, copy, add) used a nop comment that is a single arg
  // where as all the other instructions used a two arg comment string. This
  // function implements the single arg version.