/usr/pkgsrc/graphics/libart #> make show-downlevel
  WARNING: This make target (show-downlevel) is about to be removed. Since you used
  WARNING: it, it may not be completele useless.  Please tell us on the
  WARNING: tech-pkg@NetBSD.org mailing list why you think this target should
  WARNING: not be removed.

This was news to me, but maybe I haven't been paying adequate attention.

What I want is a target that explains which situation I am in:

  package is not installed
  package is installed and does not match pkgsrc
  package is installed and does match pkgsrc

Essentially this is like pkg_chk for one package.  I don't care what I
type for this, and I don't really care what the output looks like, but
of course I would prefer that it be regular and machine parseable.