code: func (cfg *Config) envNameForSpec(c context.Context, s *vpython.Spec, rt *vpython.Runtime) string {
  	uid := "<unknown>"
  	if user, err := user.Current(); err == nil {
  		uid = user.Uid
  	} else {
  		logging.Warningf(c, "Unable to find current user ID: %s", err)
  	}
  
  	name := spec.Hash(s, rt, EnvironmentVersion,
  		string(assets.GetAssetSHA256(siteCustomizePy)), uid)
  	if cfg.MaxHashLen > 0 && len(name) > cfg.MaxHashLen {
  		name = name[:cfg.MaxHashLen]
  	}
  	return name
  }
docs: // EnvName returns the VirtualEnv environment name for the environment that cfg
  // describes.