qref -d no longer sets patch dates

[Giorgos Keramidas]

The qrefresh -d option used to unconditionally set the date of a patch.
It no longer does this in crew:

  $ hg tip --template '{node|short} {date|isodate}\n'
  b34ef60e69eb 2009-01-04 19:54 +0200

  $ hg qref -d '2008-12-27 23:38:06 +0000'

  $ hg tip --template '{node|short} {date|isodate}\n'
  041a94ba3e77 2009-01-04 19:55 +0200

I haven't used the option in a while, but I seem to recall that qrefresh
could set the patch date, even if the patch didn't have one already.

Has this changed recently?  If what qrefresh does now is the correct
behavior, how should I set the patch date now?