Minor annoyance with slow completions

[Julien Nicoulaud <julien.nicoulaud@xxxxxxxxx>]

I have this (bad) habit of spamming the tab key more often than necessary,
and this leads to issues with slow completions (eg: systemd completion, did
not dig into that but sometimes completing services takes several seconds).

So sometimes I start typing something like "sudo systemctl status d<tab>",
completion hangs, I continue typing it by hand, and after a few seconds the
completion match is inserted followed by everything I typed in the
meanwhile. In a similar way, hitting tab several times after completion is
triggered produces unwished results...

I would prefer this kind of behaviour, in order of preference:
a) any keystroke after completion is started cancels completion. special
case for <tab>, which is ignored
b) any keystroke after completion is started is ignored

Did I miss something ? How would you implement that, define a new
expand-or-complete widget that unbinds keys before triggering completion ?

Cheers,
Julien