TODO, in part based on feedback from users (thanks!):

* Be better at detecting broken dependency trees; eg, if
  a package claims to depend on another package that does
  not exist.
* Make it more difficult to accidentally have pkgmanager nuke
  all packages on the first run - be clearer to the user on the
  fact that pkgmanager is about to remove packages.
* Do something about clisp constantly complaining about charsets
  on startup.
* Do something about character encoding errors (triggered by at
  least one user).
* Create some form of interactive want list editing facility
  that makes it easier for users to manage their want list. In
  particular, focus on making it easier to create an initial
  want list.
* Allow the user to proceed with only parts of the actions
  pkgmanager wants to take. E.g. - skipping package removals.
* Allow the user to manually override dirty/depupdate logic
  to avoid rebuilding huge amounts of packages when the
  user is quite certain it is not needed.
* Support a mode in which pkgmanager looks at package versions
  and allows updating only packages whose upstream versions
  have changed (and dependents).
* Have pkgmanager understand expected error conditions, such as
  unacceptable license failures etc. pkgmanager should not treat
  such failures as internal errors/bugs, as it currently does.
* Forced rebuilds of packages (e.g., libc changes in DFly), either
  specifically for certain packages or globally.
* Ability to supress pkgsrc build output and just see pkgmanager
  progress messages (combine with logging).
* Logging of pkgsrc messages (for future reference, eg save those
  containing MESSAGE output), or outputs for failed builds.
* Finer-grained control of verbosity, with a documented interface.

DONE:

* Have pkgmanager automatically add 'core' packages to the want
  list the first time it is run, and warn users when they try
  to remove them.
* Don't stupidly ask about invalidating summary cache in response
  to mk.conf changes when the user is trying to do just that
  with flush-cache.
* Consider both /etc/mk.conf and ${PREFIX}/etc/mk.conf.
* Re-evaluate how to implement the summary cache, as it is
  currently unable to reliably detect changes in the pkgsrc
  tree. Perhaps go for a manual method where the user must
  trigger an update when changes have occurred (slow).