Bug#987017: recommends 3 different ways to find obsolete packages, pick one

[Antoine Beaupré <anarcat@debian.org>]

I actually forgot that bullseye itself introduces yet another one:

    apt list ~obsolete

Apparently, those are also a thing:

     comm -23 <(dpkg-query -W -f '${db:Status-Abbrev}\t${Package}\n' | grep '^.[^nc]' | cut -f2 | sort) <(apt-cache dumpavail | sed -rn 's/^Package: (.*)/\1/p' | sort -u)
     apt list --installed | awk -F/ '/\[installed,local\]/{print $1}'

-- 
I've got to design so you can put it together out of garbage cans. In
part because that's what I started from, but mostly because I don’t
trust the industrial structure—they might decide to suppress us
weirdos and try to deny us the parts we need.
                       - Lee Felsenstein