bug#27840: 26.0.50; vc-git-grep stopped working on git master

[Tom Tromey]

I am running a build of git master from yesterday.
I tried M-x vc-git-grep.

This successfully runs the grep and puts the output into *grep*.
However, the highlighting is incorrect and M-x next-error claims there
are no grep hits.  Using C-c (compile-goto-error) in *grep* also does
not work.



In GNU Emacs 26.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
 of 2017-07-25 built on pokyo
Repository revision: 60b74190286afdc85ccf4e5042a5b89732e2a320
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:     Fedora release 25 (Twenty Five)

Recent messages:
Wrote /home/tromey/.newsrc.eld
Saving /home/tromey/.newsrc.eld...done
nnimap read 0k from imap.gmail.com
Expiring articles...done
Saving Gnus registry (92421 entries) to ~/.gnus.registry.eieio...
Saving Gnus registry (size 92421) to ~/.gnus.registry.eieio...done
Saving /home/tromey/.newsrc.eld...
Saving file /home/tromey/.newsrc.eld...
Wrote /home/tromey/.newsrc.eld
Saving /home/tromey/.newsrc.eld...done

Configured using:
 'configure --prefix=/home/tromey/Emacs/install --with-modules'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 MODULES LIBSYSTEMD

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Group

Minor modes in effect:
  erc-spelling-mode: t
  erc-truncate-mode: t
  diff-auto-refine-mode: t
  gnus-topic-mode: t
  gnus-undo-mode: t
  which-function-mode: t
  projectile-global-mode: t
  projectile-mode: t
  erc-notify-mode: t
  erc-notifications-mode: t
  erc-services-mode: t
  erc-list-mode: t
  erc-menu-mode: t
  erc-autojoin-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-netsplit-mode: t
  erc-hl-nicks-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  savehist-mode: t
  cl-old-struct-compat-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-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
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/home/tromey/.emacs.d/elpa/bubbles-0.5/bubbles hides 
/home/tromey/Emacs/install/share/emacs/26.0.50/lisp/play/bubbles

Features:
(shadow emacsbug dxr idutils gnus-html help-fns radix-tree url-cache
erc-spelling erc-truncate cursor-sensor mhtml-mode css-mode smie eww
mm-url url-queue bbdb-sc supercite regi mailalias mail-hist nnir
git-rebase-mode git-commit-mode log-edit term/xterm xterm dabbrev
copyright find-dired misearch multi-isearch smerge-mode js sgml-mode
cc-mode cc-fonts cc-guess cc-menus cc-cmds bug-reference add-log
log-view pcvs-util webjump flow-fill bbdb-gui bbdb-hooks bbdb-rmail
rmailsum vc-mtn vc-hg vc-git diff-mode vc-bzr vc-src vc-sccs vc-svn
vc-cvs vc-rcs sort gnus-cite smiley shr-color url-http url url-proxy
url-privacy url-history url-auth url-cookie url-domsuf url-gw url-expand
url-methods url-util shr svg dom browse-url mm-archive gnus-bcklg
gnus-async qp gnus-ml disp-table gnus-topic nndraft nnmh nnfolder utf-7
bbdb-gnus bbdb-snarf mail-extr bbdb-com network-stream nsm starttls
gnus-agent gnus-srvr gnus-score score-mode nnvirtual gnus-msg nntp
gnus-cache gnus-registry registry eieio-base gnus-art mm-uu mml2015
mm-view mml-smime smime dig mailcap gnus-sum gnus-group gnus-undo
smtpmail sendmail gnus-start gnus-cloud nnimap nnmail mail-source tls
gnutls utf7 netrc nnoo parse-time gnus-spec gnus-int gnus-range message
puny rfc822 mml mml-sec epa derived epg mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader gnus-win gnus
nnheader gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums
mail-utils mm-util mail-prsvr flyspell ispell diminish appt diary-lib
diary-loaddefs cal-menu calendar cal-loaddefs which-func imenu edmacro
kmacro projectile grep compile ibuf-ext ibuffer ibuffer-loaddefs
autorevert filenotify desktop frameset cus-start cus-load erc-notify
erc-desktop-notifications erc-services notifications dbus xml erc-list
erc-menu erc-join erc-ring erc-networks erc-pcomplete pcomplete
erc-track erc-match erc-netsplit erc-hl-nicks easy-mmode color
erc-button erc-fill erc-stamp wid-edit erc-goodies erc erc-backend
erc-compat format-spec thingatpt pp dired-aux dired-x dired
dired-loaddefs warnings advice vc-dir ewoc vc vc-dispatcher flycheck
cl-extra json map find-func help-mode rx subr-x dash cc-styles cc-align
cc-engine cc-vars cc-defs bbdb cl timezone ange-ftp comint ansi-color
ring server savehist finder-inf bbdb-autoloads dwarf-mode-autoloads
lisppaste-autoloads pydoc-info-autoloads info-look weblogger-autoloads
info package easymenu epg-config url-handlers url-parse auth-source
cl-seq eieio eieio-core cl-macs eieio-loaddefs password-cache url-vars
seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded 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 dbusbind inotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 3013500 1806998)
 (symbols 48 106763 55)
 (miscs 40 24752 5430)
 (strings 32 1386985 121382)
 (string-bytes 1 63141799)
 (vectors 16 114896)
 (vector-slots 8 3399404 294794)
 (floats 8 535 2243)
 (intervals 56 16523 3246)
 (buffers 992 126))