mq: upgrade non-plain patches to HG format when setting parent in patchheader

Parent will now always be updated or added when qrefreshing HG patches. Plain
patches will not be changed, but patches that neither are plain nor HG will be
upgraded to HG patches on first refresh.

hgext/mq.py

@@ -241,7 +241,9 b' class patchheader(object):'
                 patchheaderat = self.comments.index('# HG changeset patch')
                 self.comments.insert(patchheaderat + 1, '# Parent  ' + parent)
             except ValueError:
-                pass
+                if not self.plainmode:
+                    tmp = ['# HG changeset patch', '# Parent  ' + parent]
+                    self.comments = tmp + self.comments
         self.parent = parent
 
     def setmessage(self, message):

tests/test-mq-eol.t

@@ -84,6 +84,8 b' force LF'
   now at: eol.diff
   $ hg qrefresh
   $ python ../cateol.py .hg/patches/eol.diff
+  # HG changeset patch<LF>
+  # Parent  0d0bf99a8b7a3842c6f8ef09e34f69156c4bd9d0<LF>
   test message<LF>
   <LF>
   diff -r 0d0bf99a8b7a a<LF>

tests/test-mq-qpush-fail.t

@@ -23,7 +23,7 b' test qpush on empty series'
   $ echo bar > bar
   $ hg add bar
   $ hg qrefresh -m 'patch 2'
-  $ hg qnew --config 'mq.plain=true' bad-patch
+  $ hg qnew --config 'mq.plain=true' -U bad-patch
   $ echo >> foo
   $ hg qrefresh
   $ hg qpop -a