bug#50935: minibuffer-electric-default-mode interface

[Juri Linkov]

> I think instead of documenting all that, we could just delete the
> reference to `minibuffer-eldef-shorten-default' from the manual, as it
> is the same thing as `minibuffer-default-prompt-format', just with a
> different interface.  Of course, the latter is not yet perfect, but
> anywhere it isn't, that's just a bug, right?  That option would look
> like the below diff.
>
> Another option is to just add a reference to
> 'minibuffer-default-prompt-format' without any deletions, basically
> accepting that the text is not perfect and move on.
>
> A third option is to add 'minibuffer-default-prompt-format' on emacs-28,
> but make the suggested deletion on master -- which give us more time to
> get `minibuffer-default-prompt-format' up to scrap.
>
> Thoughts?

I guess the answer depends on the question how many prompts
are already converted to 'minibuffer-default-prompt-format',
and how many remain.  I checked a few commands, and noticed
only one command that doesn't use the new format.  It's 'M-.'
('xref-find-definitions').  But maybe it can't use the new option
'minibuffer-default-prompt-format' because xref.el should be
available in old versions?  Still it could use

  (if (boundp 'minibuffer-default-prompt-format) ...