Fix "Cannot determine magit's version" logs on Windows

Magit complains loudly (but harmlessly) when it can't determine its own
version in a sparse clone. This was fixed upstream in
magit/magit@b1b2683 for unix OSes, but not for Windows where symlinks
aren't supported, and so `magit-version` can't resolve its own repo's
root (see raxod502/straight.el#520).

modules/tools/magit/autoload.el

@@ -1,5 +1,27 @@
 ;;; tools/magit/autoload.el -*- lexical-binding: t; -*-
 
+;; HACK Magit complains loudly (but harmlessly) when it can't determine its own
+;;      version in a sparse clone. This was fixed upstream in
+;;      magit/magit@b1b2683, but only for macOS and Linux users. Windows doesn't
+;;      support symlinks as unix knows them, so `magit-version' can't resolve
+;;      its own repo's path.
+;;;###autoload
+(when! IS-WINDOWS
+  (defadvice! +magit--ignore-version-a (&optional print-dest)
+    :override #'magit-version
+    (when print-dest
+      (defvar magit-git-debug)
+      (princ (format "Magit (unknown), Git %s, Emacs %s, %s"
+                     (or (let ((magit-git-debug
+                                (lambda (err)
+                                  (display-warning '(magit git) err :error))))
+                           (magit-git-version t))
+                         "(unknown)")
+                     emacs-version
+                     system-type)
+             print-dest))
+    nil))
+
 ;;;###autoload
 (defun +magit-display-buffer-fn (buffer)
   "Same as `magit-display-buffer-traditional', except...