phases: prevent mq to qimport immutable change.

hgext/mq.py

@@ -1765,6 +1765,9 b' class queue(object):'
 
             diffopts = self.diffopts({'git': git})
             for r in rev:
+                if not repo[r].mutable():
+                    raise util.Abort(_('revision %d is not mutable') % r,
+                                     hint=_('see "hg help phases" for details'))
                 p1, p2 = repo.changelog.parentrevs(r)
                 n = repo.changelog.node(r)
                 if p2 != nullrev:

tests/test-mq-qimport-fail-cleanup.t

@@ -32,3 +32,9 b' valid patches before fail added to serie'
 
   $ hg qseries
   b.patch
+
+  $ hg pull -q -r 0 . # update phase
+  $ hg qimport -r 0
+  abort: revision 0 is not mutable
+  (see "hg help phases" for details)
+  [255]