Dump all undo tree history files in one directory

.emacs.d/init.el

@@ -477,7 +477,9 @@
   :config
   (bind-key "M-/" 'undo-tree-visualize)
   (global-undo-tree-mode)
-  (setq undo-tree-enable-undo-in-region nil))
+  (setq undo-tree-enable-undo-in-region nil
+        undo-tree-history-directory-alist
+        `(("." . ,(concat user-emacs-directory "undo-tree-hist")))))
 
 (use-package hydra :ensure :demand
   :config

.gitignore

@@ -31,3 +31,4 @@
 /.emacs.d/eshell/history
 /.emacs.d/eaf/
 /.emacs.d/recentf
+/.emacs.d/undo-tree-hist/