about mq qpop -f

[Ling, Xiaofeng]

Chris
     currently, if using hq qpop -f, it will report errors and
hg parents also fails.
After such a patch, it is ok. What's issue?

--- hgext/mq.py 2005-11-20 21:34:02.000000000 +0800
+++ /usr/lib/python2.3/site-packages/hgext/mq.py        2005-11-24 
09:30:13.621459792 +0800
@@ -556,6 +556,7 @@
                  except: pass
              if a:
                  repo.dirstate.forget(a)
+            repo.changes(None, None)
              repo.dirstate.setparents(*pp)
              cache[pp[0]] = (top, c, a, d, u)
          self.strip(repo, rev, update=False, cache=cache)