I have never seen this personally, because the first thing to do if you haven't upgraded Arch in a long time is check archlinux.org where they list right in the

I have never seen this personally, because the first thing to do if you haven't upgraded Arch in a long time is check archlinux.org where they list right in the front page any breaking update, which are quite rare and they provide the exact steps to proceed. Or just install informant from AUR, to force you to read the Archlinux package news before proceeding with any pacman operation.