Accessing undo/redo list

[hommes-doutant]

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

Ij my application, I need to track if the code has been modified since last save.

To implement it, the less expensive way to do so is to access the current undo/redo element (by id or hash of the object), and then checking against it when the undo/redo history changes.

There are other ways to track it, but they would be redundant with the redo history or would be used as fallback in case something is wrong with the undo/redo.

Otherwise it would be nice to provide a custom, undo/redo history controller to the code line editing controller, that can be customised.