incorrect working revision for the mercurial VC backend

[Nick Roberts]

 > I believe using the "hg parent" command is more accurate in computing
 > the working revision:
 > 
 >     hg parent --template "{rev}" FILE
 > 
 > Also by using the --template option, the command will return just the
 > revision number, making the `string-match' call unnecessary.

To get some practice with bzr, I've pushed the change below.  Can you please
tell me if it DTRT for you?

-- 
Nick                                           http://users.snap.net.nz/~nickrob


2009-12-30  Nick Roberts  <address@hidden>

        Show working revision correctly for mercurial.
        * vc-hg.el (vc-hg-working-revision): Use hg parent instead of
        hg log as suggested by Alex Harsanyi <address@hidden>,


=== modified file 'lisp/vc-hg.el'
*** lisp/vc-hg.el       2009-12-14 17:12:18 +0000
--- lisp/vc-hg.el       2009-12-30 02:22:45 +0000
*************** If nil, use the value of `vc-diff-switch
*** 209,222 ****
                        ;; Ignore all errors.
                        (process-file
                         "hg" nil t nil
!                        "log" "-l1" (file-relative-name file)))
                      ;; Some problem happened.  E.g. We can't find an `hg'
                      ;; executable.
                      (error nil)))))))
!     (when (eq 0 status)
!       (if (string-match "changeset: *\\([0-9]*\\)" out)
!           (match-string 1 out)
!         "0"))))
  
  ;;; History functions
  
--- 209,219 ----
                        ;; Ignore all errors.
                        (process-file
                         "hg" nil t nil
!                        "parent" "--template" "\"{rev}\"" (file-relative-name 
file)))
                      ;; Some problem happened.  E.g. We can't find an `hg'
                      ;; executable.
                      (error nil)))))))
!     (when (eq 0 status) (read out))))
  
  ;;; History functions