$ apt-cache dumpavail | grep '^Provides: x-window-manager' -B 11
$ apt-cache dumpavail | grep '^Provides: x-window-manager' -B 11 | grep '^Package:'
$ apt-cache dumpavail | grep '^Provides: x-window-manager' -B 11 | grep '^Package:' | awk -F ': ' '{print $2}' | sed 's/, /\n/g' | sort -u
$ apt-cache dumpavail | grep '^Provides: x-window-manager' -B 11 | grep '^Package:' | awk -F ': ' '{print $2}' | sed 's/, /\n/g' | sort -u | awk '{printf "* [%s](https://packages.ubuntu.com/bionic/%s)\n", $1, $1}'
$ apt-cache dumpavail | grep '^Provides: x-window-manager' -B 11 | grep '^Package:' | awk -F ': ' '{print $2}' | sed 's/, /\n/g' | sort -u | awk '{printf "* [%s](https://packages.ubuntu.com/bionic/%s)\n", $1, $1}' > x-window-manager.md