Check if current user undoing/redoing?

Question

Is there a way so that the Emacs are able to tell if the current user is undoing/redoing in the current buffer?

Here is the task I want to accomplish, I have add a hook to after-change-function, it all works out great exclusive of when I hit undo/redo this hook get called too. And this is what I want to avoid... Is there other way to get around this issue?

Answer 1

C-hv undo-in-progress

Documentation:
Non-nil while performing an undo.
Some change-hooks test this variable to do something different.

Bearing in mind that "redoing" is really still "undoing" in Emacs, this ought to cover all cases.