code: func checkVersion(cReg registry.ClusterRegistry) (string, bool) {
  	fv := version.SemVersion
  	lv, err := cReg.LatestDaemonVersion()
  	if err != nil {
  		log.Errorf("error attempting to check latest fleet version in Registry: %v", err)
  	} else if lv != nil && fv.LessThan(*lv) {
  		return fmt.Sprintf(oldVersionWarning, fv.String(), lv.String()), false
  	}
  	return "", true
  }
docs: // checkVersion makes a best-effort attempt to verify that fleetctl is at least as new as the
  // latest fleet version found registered in the cluster. If any errors are encountered or fleetctl
  // is >= the latest version found, it returns true. If it is < the latest found version, it returns
  // false and a scary warning to the user.