magit-version: Handle Straight's fake symlinks

Add a new function `magit--straight-chase-links' to do so.
Closes radian-software/straight.el#520.

lisp/magit.el

@@ -389,6 +389,20 @@ is run in the top-level directory of the current working tree."
   "The version of Magit that you're using.
 Use the function by the same name instead of this variable.")
 
+(defun magit--straight-chase-links (filename)
+  "Chase links in FILENAME until a name that is not a link.
+This is the same as `file-chase-links', except that it also
+handles fake symlinks that are created by the package manager
+straight.el on Windows.
+
+See <https://github.com/raxod502/straight.el/issues/520>."
+  (when (and (bound-and-true-p straight-symlink-emulation-mode)
+             (fboundp 'straight-chase-emulated-symlink))
+    (when-let ((target (straight-chase-emulated-symlink filename)))
+      (unless (eq target 'broken)
+        (setq filename target))))
+  (file-chase-links filename))
+
 ;;;###autoload
 (defun magit-version (&optional print-dest)
   "Return the version of Magit currently in use.
@@ -403,15 +417,15 @@ and Emacs to it."
     (unless (and toplib
                  (equal (file-name-nondirectory toplib) "magit.el"))
       (setq toplib (locate-library "magit.el")))
-    (setq toplib (and toplib (file-chase-links toplib)))
+    (setq toplib (and toplib (magit--straight-chase-links toplib)))
     (push toplib debug)
     (when toplib
       (let* ((topdir (file-name-directory toplib))
              (gitdir (expand-file-name
                       ".git" (file-name-directory
                               (directory-file-name topdir))))
              (static (locate-library "magit-version.el" nil (list topdir)))
-             (static (and static (file-chase-links static))))
+             (static (and static (magit--straight-chase-links static))))
         (or (progn
               (push 'repo debug)
               (when (and (file-exists-p gitdir)