From Gentoo Wiki
"mergence" is Digit's gentoo maintenance scripts.
- a script to update and maintain gentoo.
- includes a world emerge, and more
- revdep-rebuild, eclean, etc-update, emaint, haskell updater...
- + layman, eix-sync, glsa-check
- previews the main bulk of what mergence would do.
- just the world emerge preview,
does not include preview of haskell updates etc.