bug#38265: 26.3; lock file is too easy to steal

[Juri Linkov]

> The default ask-user-about-lock is too easy to miss.
>
> For example, if one were typing "asparagus", they would likely steal the
> lock without even realizing that it happened (the "a" triggers the
> prompt on buffer modification and the "s" steals the lock).
>
> It would be nice to have the prompt be harder to hit accidentally, such
> as making all of the keys uppercase or having to type them out like
> yes/no (but the latter might be too heavyweight).  Or the prompt should
> have a short timeout before allowing the user to respond (like how
> yes-or-no-p does when you provide an invalid response).

On the request in 
https://lists.gnu.org/archive/html/emacs-devel/2019-11/msg00517.html
recently ‘(discard-input)’ was removed from ‘read-char-from-minibuffer’.
Should it be put back?

ask-user-about-supersession-threat uses read-char-from-minibuffer, so if
it contained ‘(discard-input)’ it could benefit from discarding such
inadvertent input as "s".

But what about the case of keyboard macros like in the link above?
What if the user recorded a keyboard macro to input that "s" intentionally?