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
>> >> 3. check that the whole buffer was deleted before a selected
>> >>    completion candidate was inserted to the buffer:
>> >>    C-h v buffer-undo-list RET
>> >
>> > Which buffer was deleted? *scratch*?  It isn't here.
>> >
>> > And what does "C-h v buffer-undo-list RET" mean?
>> >
>> > Bottom line: I don't understand what is the bug here and/or how to
>> > reproduce it.
>>
>> The contents of the *scratch* buffer is erased and replaced
>> with the same text.  This fact can be confirmed by looking
>> at the value of 'buffer-undo-list' that contains the text
>> of the whole buffer as a string.  Especially this is noticeable
>> when using in-region completion in a large buffer.
>>
>> With the patch, only the completed string is inserted.
>
> Thanks for the explanation.  Then please install this on master, since
> AFAIU this is a very old problem, and it's just an aesthetic one.

Actually, this is not an old problem.  It's in a new feature added in 29.1.
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.