No, they're not universal, but 99.99+% of source trees do not directly reference files outside of the source tree. i've never personally seen even one which does (and i've seen a boatload of source trees).

In any case - i've come to accept that Geany's project file is but a convenience for remembering what i was editing, and not a real "project file" (it doesn't know how to build my project - GNU make does that for me). And given that scope, it's absolute-path behaviour doesn't bother me all that much any more. But i do think the solution mentioned by Jiri and others would be "the right thing to do."

i wouldn't think of it :).