bug#40919: 27.0.91; next-error-select-buffer does not always behave as documented

[Dmitry Gutov]

On 04.05.2020 01:36, Juri Linkov wrote:
> Another variant would be
> to add an optional choice to the existing option that allows to restore
> the old behavior and doesn't affect the current behavior in any way.

FWIW, I'd consider that more of a documentation change.

More importantly, and certainly only for Emacs 28, Juri could you remind 
me what we'll be losing by removing the case no. 2 from 
next-error-find-buffer?

The ability to switch to an arbitrary Grep buffer and start using it 
with 'M-x next-error'? E.g. if there are several of them. That's more of 
a backward compatibility concern, right? Or do you have scenarios in 
mind where this will really save on keystrokes?

On another note, perhaps we could add a message to 
next-error-select-buffer that would be shown if we suspect this command 
will not have the expected result for the user.