bug#51501: 28.0.60; shell-quote-argument quotes "^!" incorrectly on MS-Windows

[Eli Zaretskii]

Observe:

  (shell-quote-argument "foo")
    => "\"foo\""

This is OK.

  (shell-quote-argument "foo^")
    => "\"foo^\""

Also OK.

  (shell-quote-argument "foo^!")
    => "^\"foo^^^!^\""

This is definitely NOT okay.

This problem gets in the way when invoking Git from Emacs, where
"abcdef^!"  has special meaning.

I'd prefer shell-quote-argument not to handle the tricky issue of "^"
at all on MS-Windows.  It is basically impossible to get that right,
especially if the command invoked with the quoted string is a batch
file, or a batch file that calls another batch file, because each
invocation of a batch file removes one level of "^" quoting, and
there's nothing Emacs can do with this.

In GNU Emacs 28.0.60 (build 106, i686-pc-mingw32)
 of 2021-10-30 built on HOME-C4E4A596F7
Repository revision: 3f998a3fc823df6117cfc286a557d495bc8ee11e
Repository branch: emacs-28
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure -C --prefix=/d/usr --with-wide-int --with-modules
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS XPM
ZLIB

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-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
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel dos-w32 ls-lisp disp-table
term/w32-win w32-win w32-vars term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer 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 emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads w32notify w32 lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 56990 12610)
 (symbols 48 7804 1)
 (strings 16 21660 3099)
 (string-bytes 1 632817)
 (vectors 16 13635)
 (vector-slots 8 180238 12742)
 (floats 8 23 261)
 (intervals 40 294 222)
 (buffers 888 11))