bug#43519: 28.0.50; Overlay at end of minibuf hides minibuf's real content

[Gregory Heytings]

[I send this mail again, apparently it was not delivered.  I apologize if 
you receive it twice.]

> > IOW, you leave it entirely to the generic window-display code to select 
> > window-start based just on the value of point?
>
> Yes.  It seems to work very well. Even the corner case regression above 
> doesn't seem very serious and can be addressed using the 
> scroll_conservatively code.

A last note: w->start has already been set to its default value (BEGV) 
just after entering resize_mini_window(), so the else part in your patch 
is not necessary anymore.  Your code has the same effect as simply doing:

if (height > max_height) height = (max_height / unit) * unit;

in place of the "Compute a suitable window start" part.