bug#61535: 29.0.60; choose-completion erases in-region buffer

[Juri Linkov]

>> >> >> 1. type: (with-c C-M-i
>> >> >> 2. type: M-down ... M-RET
>>
>> Actually, this is not an old problem.  It's in a new feature added in 29.1.
>
> Hmmm... I don't think I see that.  Both completion-in-region-mode and
> the condition at that place haven't changed in a while.  The addition
> of completion-use-base-affixes part is new, but since it's via 'and',
> it cannot have changed what the code before did, only cause it to do
> that in fewer cases.  What am I missing?

'M-RET' above is new.  It's bound to the new function
'minibuffer-choose-completion' that let-binds
'completion-use-base-affixes' to t that works
only in the minibuffer, not in 'completion-in-region-mode'.

>> And this patch fixes the new feature.  This is different from a similar
>> problem fixed now in bug#61479 that is really an old problem.
>
> This is all undecipherable for me, sorry.  What is that "new feature",
> and how is it fixed here?

New feature is 'M-RET', 'minibuffer-choose-completion',
'completion-use-base-affixes'.  What is fixed here
is their interaction.

> And how is bug#61479 relevant?

It's an example of a bug fixed in an old feature.