Undo tree

(defhydra hydra-undo-tree (:hint nil)
  "
  _p_: undo  _n_: redo _s_: save _l_: load   "
  ("p"   undo-tree-undo)
  ("n"   undo-tree-redo)
  ("s"   undo-tree-save-history)
  ("l"   undo-tree-load-history)
  ("u"   undo-tree-visualize "visualize" :color blue)
  ("q"   nil "quit" :color blue))

(global-set-key (kbd "C-x u") 'hydra-undo-tree/undo-tree-undo)`

Every symmetric function pair should have its own hydra - undo/redo included.