Emacs: Store undo history in the cache directory

.config/emacs/config/evil.org

@@ -11,7 +11,10 @@ Evil mode and related packages.
 
 #+BEGIN_SRC emacs-lisp
 (use-package undo-tree
-  :config (global-undo-tree-mode))
+  :config
+  (setq undo-tree-auto-save-history t)
+  (setq undo-tree-history-directory-alist `(("." . ,(concat dot-cache-dir "/undo-tree"))))
+  (global-undo-tree-mode))
 
 (use-package goto-chg)