bug#37514: PATCH: Add setting to allow switching to an already-visible buffer by default

[Juri Linkov <juri@linkov.net>]

>>> 'switch-to-prev-buffer' and 'switch-to-next-buffer' are the canonical
>>> commands for navigating a specific window's buffer list (here these
>>> are bound to <M-left> and <M-right> because I don't care for word-like
>>> movement).
>>
>> Hey, those are really useful commands that I didn't know about.
>>
>> Would it make sense to give them a default key binding?
>
> Maybe Juri has an idea ...

Fortunately we already have several default key bindings for this:

C-x <C-left>, C-x <left>, <XF86Back>
C-x <C-right>, C-x <right>, <XF86Forward>

But nevertheless customizability of buffers for the C-x b prompt
could be improved.  The current gratuitous removing visible buffers from
C-x b prompt sometimes makes more harm than good.  One example case:

0. emacs -Q
1. C-h e   -- this displays *Messages* in another window

Now try to show the *scratch* buffer in another window,
the most convenient way is:

2. C-x 4 b   -- and select the current buffer *scratch*

but there is no "*scratch*" in completions of C-x 4 b,
because completions doesn't include the current buffer,
so need to type the whole string "*scratch* RET".

I don't know if a new option in the proposed patch
solves this problem as well.

Or maybe we need a more general DWIM-like customizable
preference of buffers for C-x b like dired-dwim-target
that is opposite to the default behavior of C-x b -
it prefers visible Dired buffers.