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

[Gregory Heytings via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>>> For example: would it be okay to start the display at the beginning of 
>>> the screen line where we end up after move_it_vertically_backward 
>>> returns?
>>
>> IMO, no, this would not be okay, at least not for icomplete/ido/...
>
> In that case, what I propose will have exactly the same effect as 
> setting window-start at BOB.  So I don't understand why you say that 
> this will not do.
>

Perhaps I misunderstood something, but for me "start the display at the 
beginning of the screen line where we end up after 
move_it_vertically_backward" would mean that if the prompt and the user 
input so far needs more than one line, only the last line would be 
displayed.  So instead of having, say,

Find file: <user input>
<user input>|
<completion candidates>

(where | represents the cursor) we would only have:

<user input>|
<completion candidates>