Re: How can I undo a change from a modification-hook?

[Clément Pit-Claudel]

> Technically you can, but it's a bit messy and will likely not be
> 100% reliable.  Personally, in your case, I wouldn't bother doing it,
> but here's how I'd do it otherwise:

Thanks for the answer! The context is Proof General: it's very annoying that 
running whitespace-cleanup retracts what looks like arbitrary sections of the 
buffer.

On 2017-04-26 08:26, Stefan Monnier wrote:
> [ and while
>   you're there, check that the beg/end/len is within the announces
>   beg/end stashed earlier, and if it's not just don't do anything
>   since it means the stash buffer-undo-list is likely unrelated.  ]

This part worries me.  Could you clarify when this would happen?
Not doing anything is risky, because it puts the buffer in an inconsistent 
state wrt the subprocess :/

Thanks!