code: func workdir(b *Builder, args []string, attributes map[string]bool, flagArgs []string, original string) error {
  	if len(args) != 1 {
  		return errExactlyOneArgument("WORKDIR")
  	}
  
  	// This is from the Dockerfile and will not necessarily be in platform
  	// specific semantics, hence ensure it is converted.
  	workdir := filepath.FromSlash(args[0])
  
  	if !filepath.IsAbs(workdir) {
  		current := filepath.FromSlash(b.RunConfig.WorkingDir)
  		workdir = filepath.Join(string(os.PathSeparator), current, workdir)
  	}
  
  	b.RunConfig.WorkingDir = workdir
  	return nil
  }
docs: // WORKDIR /tmp
  //
  // Set the working directory for future RUN/CMD/etc statements.
  //