Avoid questions from portupgrade?

[Kai Grossjohann]

I started a "portupgrade -avR" yesterday.  It stopped in the middle of
the night, after getting to GhostScript.  GhostScript asks me which
drivers to compile.

Is there a way, preferrably in /etc/make.conf, that I can tell it
beforehand which drivers I want, so that GhostScript won't ask?

Is there a way for me to find out which other ports like to ask
questions, which questions it asks, and to preanswer them?

tia,
Kai