priority of make/ports options (?) -- FreeBSD Port: sysutils/portconf

[martinko]

Hello,

I'm using portconf to set ports' knobs.  Also I'm setting some general
knobs via make.conf.

Now I've run into this situation:
- i've got WITH_GECKO=seamonkey in /etc/make.conf
- yelp from new gnome 2.16 does not build with knob above. therefore in
/usr/local/etc/ports.conf i set:
x11/yelp: WITH_MAN | WITH_INFO | USE_GECKO=xulrunner
Unfortunately it does not work as I intended -- when I `portinstall
gnome2-lite` it tries to build yelp WITH_GECKO=seamonkey. :-/

How can I solve this pls ??
How can I specify a general knob and then override it for some ports ?

Cheers,

Martin