bug#56613: 29; minibuffer-complete-history throws an error for minibuffer-history-variable=t

[Stefan Monnier]

>> I think the long-term direction is clear: `completion-at-point` should
>> be used not just "in buffer" but in the minibuffer as well.
>> We could start that journey by making use of it for CRM.
>
> Not sure if I agree with this in full generality. The question is if you
> define completion only as completion of text or if you also accept the
> selection paradigm, where are a bunch of candidates are offered and
> filtered. The selection paradigm is used in most popular applications
> (web browser history, form filling). In Emacs we have Icomplete, Ivy,
> Vertico, etc. which implement that paradigm.

I wasn't careful enough in what I wrote.  I didn't mean to say that CRM
should use the `completion-at-point` UI, but that it should rely on CAPF
as the way to complete each element.

How to make that interact correctly with packages like `icomplete-mode`
which have been designed specifically for minibuffer completion is part
of the implementation issues.


        Stefan