Make mtree(8) fail with missing/extra files?

[Taylor R Campbell <campbell+netbsd-tech-userlevel%mumble.net@localhost>]

Can mtree(8) be made to fail, i.e., return a nonzero exit status
(preferably 2), if there are any missing or extra files in the
directory tree relative to the specification?

If not, I think we should provide a way to do this.  What should the
option be called?  We may be running low on letters with mtree(8).

Alternative is to parse the output, I guess, which seems suboptimal.