>I've been trying to update a pkgsrc module and I've run into a situation
>where the best way to enable an option seems to be to optionally patch
>the source before building, using a specific patch selected from a set
>of multiple optional patches (included in say ${FILESDIR}), based on
>some setting in mk/bsd.prefs.mk and/or /etc/mk.conf.

make your patch contain all features, and then enable each feature
based on the presence of some preprocessor token.  ie, if you have a
patch that does something for alpha machines, your patch would contain
code surrounded by #ifdef alpha/#endif.

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