bug#67540: 29.1; Emacs on Windows incorrectly capitalizes some environment variables

[Dave Abrahams]

emacs -Q
M-! set

Now issue the "set" command from a CMD shell. Notice that the "Path"
environment variable has been renamed to "PATH" in Emacs.  This renaming
interferes with some tools operating correctly e.g. the swift compiler
(see https://swift.org).

I notice that the "ComSpec" variable is getting the same treatment

I am able to work around the problem as follows:

(defun unsetenv (var-name)
  (let ((current-prefix-arg '(4)))
        (funcall-interactively 'setenv var-name nil)))

(when (eq system-type 'windows-nt)
  (dolist (v '("Path" "ComSpec"))
          (let ((x (getenv v)))
               (unsetenv (upcase v))
               (setenv v x))))


In GNU Emacs 29.1 (build 2, x86_64-w64-mingw32) of 2023-08-02 built on
AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.22621
System Description: Microsoft Windows 10 Pro (v10.0.2009.22621.2715)

Configured using:
'configure --with-modules --without-dbus --with-native-compilation=aot
--without-compress-install --with-tree-sitter CFLAGS=-O2'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XPM ZLIB

(NATIVE_COMP present but libgccjit not available)

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1252

Major mode: Dired by name

Minor modes in effect:
  magit-wip-initial-backup-mode: t
  magit-wip-before-change-mode: t
  magit-wip-after-apply-mode: t
  magit-wip-after-save-mode: t
  global-git-commit-mode: t
  shell-dirtrack-mode: t
  server-mode: t
  ws-butler-global-mode: t
  ws-butler-mode: t
  global-auto-revert-mode: t
  savehist-mode: t
  delete-selection-mode: t
  override-global-mode: t
  straight-use-package-mode: t
  straight-package-neutering-mode: t
  straight-symlink-emulation-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
c:/Users/dave/.emacs.d.default/straight/build/transient/transient hides 
c:/Program Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/transient
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package hides 
c:/Program Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-lint 
hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package-lint
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-jump 
hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package-jump
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-ensure 
hides c:/Program 
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c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-diminish 
hides c:/Program 
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c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-delight 
hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package-delight
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-core 
hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package-core
c:/Users/dave/.emacs.d.default/straight/build/use-package/use-package-bind-key 
hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/use-package-bind-key
c:/Users/dave/.emacs.d.default/straight/build/bind-key/bind-key hides 
c:/Program Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/use-package/bind-key
c:/Users/dave/.emacs.d.default/straight/build/seq/seq hides c:/Program 
Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/emacs-lisp/seq
c:/Users/dave/.emacs.d.default/straight/build/let-alist/let-alist hides 
c:/Program Files/Emacs/emacs-29.1/share/emacs/29.1/lisp/emacs-lisp/let-alist

Features:
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magit-tag magit-merge magit-branch magit-reset magit-files magit-refs
magit-status magit magit-repos magit-apply sh-script smie treesit
executable swift-mode swift-mode-imenu swift-mode-repl
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yaml-mode-autoloads tide tide-lv thingatpt imenu flycheck find-func s
dash etags fileloop generator xref tide-autoloads flycheck-autoloads
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dwa-global-config compile text-property-search comint ansi-osc
ansi-color ring skeleton modus-operandi-tinted-theme modus-themes
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generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
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paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode
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cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
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charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads w32notify w32 lcms2 multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 557582 44793)
(symbols 48 31897 0)
(strings 32 115342 4566)
(string-bytes 1 3994014)
(vectors 16 67230)
(vector-slots 8 1455375 78880)
(floats 8 356 751)
(intervals 56 18883 2260)
(buffers 984 33))