What I do sometimes is 'pkg_delete \*', and then do that again until
all the packages are gone, and then fix broken +REQUIRED_BY files, and
then delete some more.  Then, I go through /usr/pkg and rm all empty
directories, and then trim by hand, leaving config files, and getting
rid of stuff that should have been deleted.


This is very similar to 'rm -rf /var/db/pkg /usr/pkg', except that it
preserves config files, points out some oddities, and takes more time.