code: func (f File) format(prefix string, last bool, _, _ int) string {
  	sym := symBranch
  	if last {
  		sym = symLeaf
  	}
  	ft := ""
  	if f.Metadata != nil {
  		switch f.Metadata["Content-Type"] {
  		case "application/octet-stream":
  			ft = " " + colBin("(binary)")
  		case "text/yaml":
  			ft = " " + colYaml("(yaml)")
  		}
  	}
  	return prefix + sym + f.Name + ft + "\n"
  }
docs: // format will format this leaf node for pretty printing