histedit: use the editor gotten by "getcommiteditor()" for "message"

Before this patch, "hg histedit" for "message" uses "ui.edit()" for
commit message editing.

It shows original commit message, but not detail about the target
revision: status of each modified/added/removed files, for example.

This patch uses the editor gotten by "getcommiteditor()" instead of
"ui.edit()" for "message"

In "test-histedit-edit.t", this patch omits "fixbundle" invocation,
because it prevents from confirming the "HG: added f" line in commit
message by filtering " added " lines.

Omiting "fixbundle" invocation causes that the exit code of "hg
histedit" appears as one of command line: in this case, "hg histedit"
is aborted by (expected) exception raising.

hgext/histedit.py

@@ -402,11 +402,10 b' def message(ui, repo, ctx, ha, opts):'
         raise error.InterventionRequired(
             _('Fix up the change and run hg histedit --continue'))
     message = oldctx.description()
-    def editor(repo, ctx, subs):
-        return ui.edit(ctx.description() + "\n", ctx.user())
     commit = commitfuncfor(repo, oldctx)
     new = commit(text=message, user=oldctx.user(), date=oldctx.date(),
-                 extra=oldctx.extra(), editor=editor)
+                 extra=oldctx.extra(),
+                 editor=cmdutil.getcommiteditor(edit=True))
     newctx = repo[new]
     if oldctx.node() != newctx.node():
         return newctx, [(oldctx.node(), (new,))]

tests/test-histedit-edit.t

@@ -240,20 +240,35 b' check saving last-message.txt, at first'
   > pretxncommit.unexpectedabort = false
   > EOF
 
+  $ hg status --rev '1fd3b2fe7754^1' --rev 1fd3b2fe7754
+  A f
+
   $ rm -f .hg/last-message.txt
-  $ HGEDITOR="sh $TESTTMP/editor.sh" hg histedit tip --commands - 2>&1 << EOF | fixbundle
+  $ HGEDITOR="sh $TESTTMP/editor.sh" hg histedit tip --commands - 2>&1 << EOF
   > mess 1fd3b2fe7754 f
   > EOF
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  adding f
   ==== before editing
   f
+  
+  
+  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
+  HG: Leave message empty to abort commit.
+  HG: --
+  HG: user: test
+  HG: branch 'default'
+  HG: added f
   ====
   transaction abort!
   rollback completed
   note: commit message saved in .hg/last-message.txt
   abort: pretxncommit.unexpectedabort hook exited with status 1
+  [255]
   $ cat .hg/last-message.txt
   f
+  
+  
   check saving last-message.txt
 
   $ cat >> .hg/hgrc <<EOF