My feature request is for the implementation of some basic set operations. Since the only sets now are system and world and system is a subset of world, the only one needed right now would be "difference". But you might as well throw in intersections, unions, whatever as well. this way, you could re-emerge your whole system (for example after a gcc upgrade) by doing emerge -e system and then emerge -e [world \minus system] (or something like that), so that you re-emerge all packages, and the system gets done first. Also, it's conceivable that sometimes someone would want to emerge world except for a few packages, so it would be nice to have a way of typing out a set from elements; for example emerge -u --deep [world \minus {openoffice}] or something like that.
*** This bug has been marked as a duplicate of 6411 ***
