bug#34535: 27.0.50; emacs -nw: while-no-input + sit-for + <KEY> => Quit

[Eli Zaretskii]

> Date: Fri, 22 Feb 2019 22:09:29 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 34535@debbugs.gnu.org
> 
> > Date: Fri, 22 Feb 2019 18:08:58 +0200
> > From: Eli Zaretskii <eliz@gnu.org>
> > Cc: 34535@debbugs.gnu.org
> > 
> > What happens on master is this: when sit-for is called inside
> > while-no-input on a TTY, it returns the cons cell (t . ?\C-g), which
> > then causes keyboard quit right after while-no-input returns.
> 
> I forgot to tell that sit-fore returns that cons cell because
> read-event returns ?\C-g, regardless of what you type, when it is
> called inside while-no-input.

To be even more accurate: sit-for pushes that cons cell onto
unread-command-events, and then the command loop reads it and triggers
keyboard quit.