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I just want to erase history here - the very last entry. This shouldn't be dangerous, right?

I figured I need to somehow transform (undo-tree-current buffer-undo-tree) and pass that to undo-tree-snip-node but I don't see exactly how to do that.

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  • Do you want to undo your last entry and return to your previous state and then erase that last entry; or, do you want to keep your current state and tell undo-tree to just forget about how you got there? Inasmuch as undo-tree just creates a new branch when you undo and then go somewhere else, why (if you don't mind explaining) would you want to erase the last entry (e.g., a use case example)?
    – lawlist
    Commented Jun 8, 2020 at 17:49
  • @lawlist I just want to forget how I got to that state. I am making an evil motion for paredit-kill. The way I do it is do the kill, then paste the killed text where it was, pop the kill ring, save the (point) for use as a motion. For simplicity, I set a handle to (prepare-change-group) before these and do (undo-amalgamate-change-group handle) afterwards so that I have just one unnecessary undo event. I tried to use undo-tree-undo, but that doesn't play well with evil - it cancels the operator which was pressed before the motion (like d). Commented Jun 8, 2020 at 18:24
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    Other than Dr. Cubitt (the author of undo-tree.el), a regular forum participant named Tobias is probably the most familiar with the data structure of the buffer-undo-tree of the undo-tree.el library. One idea would be to save a copy of the list using copy-tree* (in the following link) before doing your stuff and then restore the list when you finish: emacs.stackexchange.com/a/32230/2287 Off hand, I do not know how to just snip off the last entry -- but, perhaps Tobias or another forum participant does ... or they can suggest an alternative approach that best suits your needs.
    – lawlist
    Commented Jun 9, 2020 at 4:23
  • @lawlist Oh, man. I think I will just rewrite the paredit-kill instead, looks like less trouble after all. But thanks for the directions and the link! Commented Jun 9, 2020 at 9:51

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