I'd like to implement the following behavior for the up-button:

* If an instance of the parent activity is on the back stack, return to the top-most instance of that parent activity.
* If there is no instance of the parent activity on the back stack, create a new instance.

Actually, when I first read about the difference between up and back, this behaviors was what I expected as default. However, I have seen now, that `NavUtils.navigateUpFromSameTask(this);` always creates a new instance of the parent activity, ignoring the fact, that there is one readily available on the back stack.

Thanks for any advice.