Backport: Fix xref-clear-marker-stack refactoring mistake

* lisp/progmodes/xref.el (xref-clear-marker-stack):
Clear the history correctly.  Changing a lexical variable has no effect.

(cherry picked from commit dfdc0f5fb7b10e737c3c8e2bdb1eb873a1e91bd7)

diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 916d83d407b15c62d4e8fe5692d2ac85336ba1fb..4db0df6c3b8c6417c47f8ce7481d8aa48f40ce81 100644 (file)
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -568,7 +568,8 @@ This can be used from `xref-after-jump-hook', for instance.")
     (dolist (l (list (car history) (cdr history)))
       (dolist (m l)
         (set-marker m nil nil)))
-    (setq history (cons nil nil)))
+    (setcar history nil)
+    (setcdr history nil))
   nil)
 
 ;;;###autoload