mainly
   as a way of using tar to extract a new pkgsrc.tar.gz over an existing
   pkgsrc tree.

Hmm.  I thought it was mostly to catch people who weren't using "sup
-o" or its moral equivalent to update pkgsrc.

I think exiting on error in this case is more likely to keep things
reliable (and keep crud from building up in people's pkgsrc trees) in
the long run.

						- Bill