vundo: add diff display

lisp/mitch-packages.el

@@ -184,7 +184,29 @@
   :if (< (string-to-number emacs-version) 28)
   :diminish)
 (use-package vundo
-  :custom (vundo-glyph-alist vundo-unicode-symbols))
+  :custom (vundo-glyph-alist vundo-unicode-symbols)
+  :config
+  ;; taken from https://github.com/casouri/vundo/issues/56
+  (defun my/vundo-diff ()
+    (interactive)
+    (let* ((orig vundo--orig-buffer)
+	   (source (vundo--current-node vundo--prev-mod-list))
+	   (dest (vundo-m-parent source)))
+      (if (or (not dest) (eq source dest))
+	  (message "vundo diff not available.")
+	(let ((buf (make-temp-name (concat (buffer-name orig) "-vundo-diff"))))
+	  (vundo--move-to-node source dest orig vundo--prev-mod-list)
+	  (with-current-buffer (get-buffer-create buf)
+	    (insert-buffer orig))
+	  (vundo--refresh-buffer orig (current-buffer) 'incremental)
+	  (vundo--move-to-node dest source orig vundo--prev-mod-list)
+	  (vundo--refresh-buffer orig (current-buffer) 'incremental)
+	  (diff-buffers buf orig)
+	  (kill-buffer buf)))))
+  :general
+  (general-define-key
+   :keymaps 'vundo-mode-map
+   "d" 'my/vundo-diff))
 (use-package evil-goggles
   :diminish
   :after evil