bug#32607: 27.0.50; pop-to-buffer in next-error-no-select

[Juri Linkov <juri@linkov.net>]

>> The special case is in next-error-no-select.  Its purpose is to display
>> the next-error buffer (the buffer with the location of the next-error),
>> not to display next-error-last-buffer (the buffer with the list of errors)
>> because next-error-last-buffer is already displayed.  The user runs
>> next-error-no-select from the selected window that already displays
>> next-error-last-buffer, there is no need to try and display the same
>> buffer again.  This behavior is not even documented.
>
> Can we please document all this?  I don't see how could anyone glean
> all that from the available documentation.
>
> And I think it's high time to have next-error facilities described in
> all pertinent details in the ELisp manual.  It is way too complex and
> powerful not to be mentioned there even as a hint.

Whereas I helped to develop the next-error framework, I'm not its author,
so I don't know the purpose of some parts, for example, I had no idea
why next-error-no-select was implemented this way.  I see that
next-error-no-select is called from compilation-display-error,
but don't understand why in grep mode the ‘n’ key is bound directly
to next-error-no-select, but not to compilation-display-error.
Also I see a glaring question mark in the comments of grep-mode-map
asking why "\r" is bound to compile-goto-error, and unfortunately
I have no answer.