bug#21166: 24.4; vc-mode and git error on newly added file to new repository

[Ed Avis]

At the shell make an empty git working tree and add one file to it,
but without committing, then edit it in Emacs:

% mkdir test
% cd test
% git init
Initialized empty Git repository in /home/eda/test/.git/
% echo >a
% git add a
% emacs -Q a

Type some text in the buffer, save with C-x C-s, then ask for a diff
with C-x v =.  This fails with the following text at the bottom of the screen:

-UU-:----F1  a              All L1    Git@master  (Fundamental) ---
fatal: bad revision 'HEAD'

-UUU:**--F1  *vc-diff*      All L1     (Fundamental from a) ----
Running git --no-pager diff-index --exit-code -p HEAD  -- a...FAILED (status 
128)


In GNU Emacs 24.4.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.10.9)
 of 2014-11-03 on wcl-linux04.wcl.local
Configured using:
 `configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no build_alias=x86_64-redhat-linux-gnu
 host_alias=x86_64-redhat-linux-gnu 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -m64 -mtune=generic' 'LDFLAGS=-Wl,-z,relro ''

Important settings:
  value of $LC_COLLATE: C
  value of $LC_CTYPE: en_GB.UTF-8
  value of $LC_MESSAGES: en_GB.UTF-8
  value of $LC_MONETARY: en_GB.UTF-8
  value of $LC_NUMERIC: en_GB.UTF-8
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
p C-a ESC f DEL DEL DEL DEL c a t DEL DEL DEL e c h 
o SPC ' # ! / b i n / s h ' RET e c h o SPC C-a C-k 
r DEL l n SPC - s SPC / b i TAB f a TAB l TAB C-a C-k 
r m SPC . g i TAB h o TAB p r e TAB - c TAB RET l n 
SPC - s SPC / h DEL b i TAB f a TAB l TAB s e SPC . 
g i TAB h o TAB p r e - c o TAB DEL DEL DEL DEL DEL 
DEL DEL DEL RET e c h o SPC > a RET g t DEL i t SPC 
a d d SPC a RET C-x C-f a RET h e l l o RET C-x C-s 
C-x v = q C-g C-g ESC x s h e l l RET ESC > g i t SPC 
s t a t u s RET C-x 1 c d SPC . . RET r m SPC - r f 
SPC t e s t RET c d SPC t e s t C-a C-k m k d i r SPC 
t e s t RET c d SPC t e s t RET g i t SPC i n i t RET 
e c j h SPC DEL DEL DEL h SPC o > DEL DEL DEL o SPC 
> a RET g i t SPC a d d SPC a RET C-x C-f a RET y e 
s RET a C-x C-s C-x v = C-x b RET C-x 1 C-x b a RET 
ESC x r e p o r t SPC e SPC b RET

Recent messages:
Finding changes in /home/eda/test/a...
vc-do-command: Running git --no-pager diff-index --exit-code -p HEAD  -- 
a...FAILED (status 128)
call-interactively: Buffer is read-only: #<buffer *vc-diff*>
Quit [2 times]
Mark set
~ 
~/test 
Saving file /home/eda/test/a...
Wrote /home/eda/test/a
Finding changes in /home/eda/test/a...
vc-do-command: Running git --no-pager diff-index --exit-code -p HEAD  -- 
a...FAILED (status 128)

Load-path shadows:
None found.

Features:
(shadow sort emacsbug sendmail apropos vc-bzr vc-sccs vc-svn vc-cvs
vc-rcs rect macros debug network-stream starttls tls mail-extr etags
sh-script smie executable smerge-mode edmacro kmacro sql view mule-util
python json dired tabify imenu man help-mode log-view diff-mode vc
vc-dispatcher cus-edit wid-edit cus-start cus-load perl-mode dabbrev
nxml-uchnm rng-xsd xsd-regexp rng-cmpct rng-nxml rng-valid rng-loc
rng-uri rng-parse nxml-parse rng-match rng-dt rng-util rng-pttrn nxml-ns
nxml-mode nxml-outln nxml-rap nxml-util nxml-glyph nxml-enc xmltok ffap
thingatpt url-parse auth-source eieio eieio-core gnus-util
password-cache url-vars misearch multi-isearch vc-git pcmpl-unix xterm
time-date log-edit easy-mmode message format-spec rfc822 mml mml-sec
mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mailabbrev mail-utils gmm-utils mailheader
pcvs-util add-log server csharp-mode advice help-fns byte-opt bytecomp
byte-compile cconv cc-langs cc-mode cc-fonts easymenu cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs zoom-frm frame-cmds
frame-fns cl-macs avoid cl gv cl-loaddefs cl-lib compile shell pcomplete
comint ring ansi-color tooltip electric uniquify 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 prog-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 nadvice
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
gfilenotify dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 2123160 189079)
 (symbols 48 30370 0)
 (miscs 40 1280 7066)
 (strings 32 74802 19252)
 (string-bytes 1 3893095)
 (vectors 16 42168)
 (vector-slots 8 1773808 319851)
 (floats 8 1683 1258)
 (intervals 56 365598 3016)
 (buffers 960 190)
 (heap 1024 107029 5604))

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