Make mergepatch save queue now that qpush isn't.

hgext/mq.py

@@ -417,6 +417,7 b' class queue:'
                 self.applied_dirty = 1
             if err:
                 return (err, head)
+        self.save_dirty()
         return (0, head)
 
     def patch(self, repo, patchfile):

tests/test-mq-merge

@@ -37,3 +37,6 b' hg ci -m update'
 hg manifest
 hg qpush -a -m 2>&1 | rewrite_path
 hg manifest
+
+# ensure status is correct after merge
+hg qpop -a

tests/test-mq-merge.out

@@ -9,3 +9,4 b' merging with queue at: .hg/patches.1'
 applying rm_a
 Now at: rm_a
 b
+Patch queue now empty