bug#13004: 24.2; vc-diff from vc-log doesn't show diff before renames (for Mercurial backend).

[Oleksandr Gavenko <gavenkoa@gmail.com>]

As always:

  $ emacs -Q

Next I open any file from Mercurial repo which is "hg mv" or "hg cp".

If you build history "C-x v l" and try to look diff (log-view-diff or "d") for
changeset before rename you get message, like:

  Finding changes in /home/user/devel/my-devel/gadict/en-pronunciation_ru.rst...
  No changes between 214 and 215

while:

  $ hg diff -r 215 en-pronunciation_ru.rst

  diff --git a/en-spelling_ru.rst b/en-pronunciation_ru.rst
  copy from en-spelling_ru.rst
  copy to en-pronunciation_ru.rst
  --- a/en-spelling_ru.rst
  +++ b/en-pronunciation_ru.rst
  @@ -1,5 +1,4 @@
   .. -*- coding: utf-8 -*-
  -
   .. include:: header.rst

   ===================


In GNU Emacs 24.2.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.10)
 of 2012-09-09 on trouble, modified by Debian

Also reproduced in GNU Emacs 24.2.50.1 (x86_64-unknown-linux-gnu, GTK+ Version
2.24.10):

  $ bzr info -v

  Related branches:
    parent branch: bzr://bzr.savannah.gnu.org/emacs/emacs-24/

  Branch history:
    110934 revisions
     10084 days old
   first revision: Thu 1985-04-18 00:48:29 +0000
  latest revision: Wed 2012-11-21 21:28:14 +0200

I expect that vc-view-diff follow history on copy as this do original CLI
client "hg".

-- 
Best regards!