code: func (podStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList {
  	errorList := validation.ValidatePod(obj.(*api.Pod))
  	errorList = append(errorList, validation.ValidatePodUpdate(obj.(*api.Pod), old.(*api.Pod))...)
  	errorList = append(errorList, validation.ValidateConditionalPod(obj.(*api.Pod), old.(*api.Pod), field.NewPath(""))...)
  	return errorList
  }
docs: // ValidateUpdate is the default update validation for an end user.