Górny: Gentoo: profiles and keywords rather than releases

Gentoo developer Michał Górny has written a lengthy blog
post that explains how Gentoo approaches releases:

Gentoo is something of a hybrid, as it combines the best of both
worlds. It is a rolling release distribution with a single shared
repository that is available to all users. However, within this
repository we use a keywording system to provide a choice between
stable and testing packages, to facilitate both production and
development systems (with some extra flexibility), and versioned
profiles to tackle major lock-step upgrades.