Górny: Gentoo: profiles and keywords rather than releases

Gentoo developer Micha Gorny has written a lengthy blogpost that explains how Gentoo approaches releases:

Gentoo is something of a hybrid, as it combines the best of bothworlds. It is a rolling release distribution with a single sharedrepository that is available to all users. However, within thisrepository we use a keywording system to provide a choice betweenstable and testing packages, to facilitate both production anddevelopment systems (with some extra flexibility), and versionedprofiles to tackle major lock-step upgrades.