bug#26066: 26.0.50; vc-git-status gives wrong result

[Jonathan Ganc <jonganc@gmail.com>]

**To reproduce:**

First, we create a simple git repository in a shell:
   $ mkdir -p ~/Desktop/temp
   $ cd ~/Desktop/temp
   $ git init
   $ echo abc > file.txt
   $ git add . && git commit -a -m "Init"

You can verify that the repository is up to date by running, e.g. 'git 
status'.

Next, we load emacs -Q and run the following:
(progn
   (setq default-directory "/")
   (require 'vc-git)
   (vc-git-state "/home/ganc/Desktop/temp/file.txt"))

The response is `added'. It should be `up-to-date'.

**Notes**


I get this same behavior on emacs 24.5, 25.1. I have some ideas about
how to fix the problems but I want to make sure this isn't somehow the
expected behavior.


In GNU Emacs 26.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.20.9)
  of 2017-03-10 built on lcy01-22
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:    Ubuntu 16.10

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
  'configure --build=x86_64-linux-gnu --prefix=/usr
  '--includedir=${prefix}/include' '--mandir=${prefix}/share/man'
  '--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var
  --disable-silent-rules '--libdir=${prefix}/lib/x86_64-linux-gnu'
  '--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode
  --disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib
  --program-suffix=-snapshot --with-modules=yes --with-x=yes
  --with-x-toolkit=gtk3 --with-xwidgets=yes 'CFLAGS=-g -O2
  -fdebug-prefix-map=/build/emacs-snapshot-rvTCtk/emacs-snapshot-93192-26848af-emacs=. -fstack-protector-strong
  -Wformat -Werror=format-security' 'CPPFLAGS=-Wdate-time
  -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES XWIDGETS LIBSYSTEMD

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

Major mode: Lisp Interaction

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-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
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   line-number-mode: t
   transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message puny seq byte-opt subr-x gv
bytecomp byte-compile cl-extra help-mode cconv cl-loaddefs pcase cl-lib
dired dired-loaddefs format-spec rfc822 mml easymenu mml-sec
password-cache epa derived epg epg-config gnus-util rmail rmail-loaddefs
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils 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 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 xwidget-internal move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 96617 5698)
  (symbols 48 20192 1)
  (miscs 40 48 115)
  (strings 32 17613 4552)
  (string-bytes 1 565163)
  (vectors 16 14650)
  (vector-slots 8 482994 4091)
  (floats 8 48 68)
  (intervals 56 241 0)
  (buffers 976 11))