bug#22860: 24.3; hg merge not too functional

[Ross Boylan]

C-x v d
put me in version  control dired mode for a mercurial-controlled
directory.
C-x v m then says
Running "hg merge"...
abort: branch 'logit' has one head - please merge with an explicit rev
(run 'hg heads' to see all heads)

It doesn't seem there's any way to specify the merge target.
I am not prompted for it, even if using C-u as a prefix.

vc.el says
;; - merge-branch ()
;;
;;   Merge another branch into the current one, prompting for a
;;   location to merge from.
;;

but in vc-hg.el that  does not seem to be the behavior.
This is probably a known problem, since the header on vc-hg.el has
;; - merge (file rev1 rev2)                    NEEDED
This comment remains in the latest git revision.

In GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.10.7)
 of 2014-03-07 on lamiak, modified by Debian
System Description:     Ubuntu 14.04.4 LTS

Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--build' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 
'--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/x86_64-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk3' '--with-toolkit-scroll-bars'
 'build_alias=x86_64-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro'
 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
G M C-g # # SPC n e w SPC d a y RET d a t e ; SPC h 
g SPC h e a d s RET C-x v d RET C-x v m C-u C-x v m 
C-h c C-x v m C-h f v c - m e r g e RET C-x o ESC O 
B ESC O C ESC O C RET ESC [ 6 ~ ESC [ 5 ~ C-s v c - 
m e r g e C-s - b C-s C-s C-s C-s C-s C-g C-g ESC O 
A ESC O A ESC O A ESC O A ESC O A ESC O A ESC O A ESC 
O A ESC O A ESC O A ESC O C ESC O C ESC O C ESC O C 
ESC O C ESC O C ESC O C C-r v c - c a l l - b a c k 
e n d C-r C-r C-r C-r C-r RET C-r d e f u n SPC v c 
- c a l l C-s C-s C-s ESC < C-s v c - c a l l - b a 
c k e n d C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s 
C-s ESC < ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ ESC [ 6 ~ ESC 
[ 6 ~ C-x C-f v c - h g TAB RET C-s d e f u n SPC m 
e r DEL DEL DEL v c - m e r g e RET C-s m e r g e - 
b r ESC < ESC [ 6 ~ ESC [ 5 ~ ESC x r e p o r t - b 
u g RET

Recent messages:
uncompressing vc.el.gz...done
Note: file is write protected
Quit
Mark saved where search started [2 times]
Mark set
Mark saved where search started
Mark set
uncompressing vc-hg.el.gz...done
Note: file is write protected
Mark saved where search started [2 times]

Load-path shadows:
/usr/share/emacs/24.3/site-lisp/debian-startup hides 
/usr/share/emacs/site-lisp/debian-startup

Features:
(shadow sort gnus-util mail-extr emacsbug message rfc822 mml mml-sec
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils find-func vc-git vc-bzr vc-sccs vc-svn vc-cvs vc-rcs vc-dir
ewoc vc vc-dispatcher help-mode misearch multi-isearch dired ediff-merg
ediff-diff ediff-wind ediff-help ediff-util ediff-mult ediff-init ediff
server jka-compr info vc-hg ido ess-toolbar ess-mouse mouseme thingatpt
browse-url ess-menu ess-swv ess-noweb ess-noweb-font-lock-mode
ess-bugs-l essd-els ess-sas-d ess-sas-l ess-sas-a shell pcomplete
ess-sta-d ess-sta-l cc-vars cc-defs make-regexp ess-sp6-d ess-sp3-d
ess-julia ess-r-d compile ess-tracebug format-spec ess-roxy advice
cl-lib advice-preload hideshow ess-help ess-developer ess-r-args eldoc
help-fns ess-s-l ess ess-inf comint ansi-color ring ess-mode
ess-noweb-mode ess-utils time-date ess-custom executable easymenu
ess-compat ess-site emacs-goodies-el emacs-goodies-custom
emacs-goodies-loaddefs easy-mmode tooltip ediff-hook vc-hooks
lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image regexp-opt
fringe tabulated-list newcomment lisp-mode register page menu-bar
rfn-eshadow timer select scroll-bar mouse jit-lock font-lock syntax
facemenu font-core frame cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese hebrew greek romanian slovak
czech european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
make-network-process dbusbind dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)