code: func SetupConfigWithNotaryURL(t *testing.T, path, notaryURL string) fs.Dir {
  	t.Helper()
  	dir := fs.NewDir(t, path, fs.WithMode(0700), fs.WithFile("config.json", fmt.Sprintf(`
  	{
  		"auths": {
  			"registry:5000": {
  				"auth": "ZWlhaXM6cGFzc3dvcmQK"
  			},
  			"%s": {
  				"auth": "ZWlhaXM6cGFzc3dvcmQK"
  			}
  		},
  		"experimental": "enabled"
  	}
  	`, notaryURL)), fs.WithDir("trust", fs.WithDir("private")))
  	return *dir
  }
docs: //SetupConfigWithNotaryURL creates a config.json file for testing in the given path
  //with the given notaryURL