Make undo-tree possible to disable

[ryukinix]

Is your feature request related to a problem? Please describe.

I'm considering replacing undo-tree with vundo due performance issues.

Describe the solution you'd like

Make possible to disable undo-tree, which is enabled by default.

Describe alternatives you've considered

Create a variable to toggle if undo-tree should be enabled, around these lines:

https://github.com/bbatsov/prelude/blob/master/core%2Fprelude-editor.el#L361-L368

It can be enabled by default to be a backward compatible change, but it should be possible to customize on user personal config.

[ryukinix]

I can do this if there is no objections.

[github-actions]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed soon if no further activity occurs. Thank you for your contribution and understanding!

[ryukinix]

I'm waiting for someone feedback to properly implement that, but it seems is not something interesting to anyone, so probably I'll only change things for me.

[bbatsov]

A configuration variable is a good approach IMO. (and it's consistent with how we normally do things)

[ryukinix]

Ok @bbatsov, opened at #1428