mq: fix qpop of working directory parent patch when not at qtip

mq assumed that it had to update from qtip to qparent, and instead of updating
from where it was it failed with:
  abort: working directory revision is not qtip

hgext/mq.py

@@ -1406,8 +1406,6 b' class queue(object):'
             self.applieddirty = True
             end = len(self.applied)
             rev = self.applied[start].node
-            if update:
-                top = self.checktoppatch(repo)[0]
 
             try:
                 heads = repo.changelog.heads(rev)
@@ -1428,7 +1426,7 b' class queue(object):'
             if update:
                 qp = self.qparents(repo, rev)
                 ctx = repo[qp]
-                m, a, r, d = repo.status(qp, top)[:4]
+                m, a, r, d = repo.status(qp, '.')[:4]
                 if d:
                     raise util.Abort(_("deletions found between repo revs"))
 

tests/test-mq-qgoto.t

@@ -46,20 +46,35 b' Using index:'
   applying c.patch
   now at: c.patch
 
-No warnings when using index:
+No warnings when using index ... and update from non-qtip and with pending
+changes in unrelated files:
 
   $ hg qnew bug314159
   $ echo d >> c
   $ hg qrefresh
   $ hg qnew bug141421
-  $ echo e >> c
+  $ echo e >> b
   $ hg qrefresh
 
+  $ hg up -r bug314159
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo f >> a
+  $ echo f >> b
+  $ echo f >> c
+
   $ hg qgoto 1
+  abort: local changes found, refresh first
+  [255]
+  $ hg qgoto 1 -f
   popping bug141421
   popping bug314159
   popping c.patch
   now at: b.patch
+  $ hg st
+  M a
+  M b
+  ? c.orig
+  $ hg up -qCr.
 
   $ hg qgoto 3
   applying c.patch