bug#39822: 27.0.90; Cannot set *Completions* buffer height using display-buffer-alist

[Juri Linkov]

>> My old opinion is that we need to try to get rid of these macros
>> and rely only on alist values.
>
> You mean 'minibuffer-completion-help' should call 'display-buffer'
> directly and do the rest of the setup manually?

Yes, and all other commands that currently use
with-displayed-buffer-window should get along without it.

>> So it would be easier to override
>> the default alist values such as 'window-height'.
>
> Is there such a default value?  Who would provide it?

Since users should be able to override it by e.g.

(add-to-list 'display-buffer-alist
             '("\\*Completions\\*"
               (window-height . 5)
               ...

a default value should have a lower priority, i.e.
in the call of 'display-buffer' in 'minibuffer-completion-help'.