[arch-general] How to detect when a package is removed from a group in pacman

Hi, recently bin86 was removed from base-devel group but the unique way I know to see this change is manually reading the pkg changelog in the arch site. The problem is simple, how to detect this change in pacman? For example, after a gnome upgrade, if a new package is added to gnome group I can do: pacman -S --needed gnome to install the missing package. But if a package is removed? How can I remove this package that doesn't belong to a group anymore? I hope you understand the question. Why not add metapackages (as for kde) for base, base-devel, gnome and gnome-extra that doesn't have this problem?