redo (ctrl+y) undo

Question

I normally undo with ctrl+_ with other editors there is a redo operation normally associated with ctrl+y. is there an emacs equivalent?

In general what is the best way to handle an "undo tree"?

Answer 1

The commentary at the outset of the undo-tree.el library describes two built-in methods to undo and redo: https://github.com/emacsmirror/undo-tree/blob/master/undo-tree.el#L87

;; C-_  C-/  (`undo-tree-undo')
;;   Undo changes.
;;
;; M-_  C-?  (`undo-tree-redo')
;;   Redo changes.

The mode key map does not follow the normal naming convention, and instead the map is named undo-tree-map. You can set up any keyboard shortcut that you want.

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Q: In general what is the best way to handle an "undo tree"?

A: Read the commentary once for a general understanding, and then read it again a second time to catch anything you may have missed the first time around. Beware that killing the visualization buffer by brute force leaves #<marker in no buffer> in the buffer-undo-tree and that causes read to choke when trying to restore from a saved history file if using the persistent save/restore feature. Older versions of the yasnippet library leave #<overlay in no buffer> inside the buffer-undo-tree that can make their way into the saved history file, which cause the same problem with persistent save/restore. [@npostavs has provided a link in the comment below to the yasnippet pull request that resolves unreadable leftovers remaining in the buffer-undo-tree.] To kill the visualization buffer, either type the letter q in the visualization buffer, or edit the parent buffer and it will close automatically -- kill-buffer is what I meant by brute force. There are some other bugs, but it is a fun library to play with. Rumor has it that someone forked it and is working on certain new features and bug fixes ....