Junio-
Thank you for the clarification. There is a lot of misleading
information about this on the Internet.
I was mistaken about when a merge driver is called. Now I see that
the merge driver is called anytime that no two of
{base,parent1,parent2} are the same. This means that a merge driver
*can* prevent a clean-but-incorrect merge. I was right that a
mergetool cannot be used to correct a clean-but-incorrect merge.
-Mike
