bug#39138: 28.0.50; Add variables for shell command output buffer names

[Robert Pluim <rpluim@gmail.com>]

>>>>> On Tue, 14 Jan 2020 23:43:00 +0100, Michael Albinus <michael.albinus@gmx.de> said:

    Michael> Tino Calancha <tino.calancha@gmail.com> writes:
    >> --- a/lisp/net/tramp.el
    >> +++ b/lisp/net/tramp.el
    >> @@ -3658,8 +3658,8 @@ tramp-handle-shell-command
    >> (current-buffer))
    >> (t (get-buffer-create
    >> (if asynchronous
    >> -		   "*Async Shell Command*"
    >> -		 "*Shell Command Output*")))))
    >> +		   shell-command-buffer-name-async
    >> +		 shell-command-buffer-name)))))
    >> (error-buffer
    >> (cond
    >> ((bufferp error-buffer) error-buffer)

    Michael> OK for me. However, I will tweak this a little bit once committed, in
    Michael> order to keep Tramp's backward compatibility. Likely like this:

    Michael> (or (bound-and-true-p shell-command-buffer-name-async) "*Async Shell Command*")

    Michael> etc. Plus a comment, which Emacs version has introduced the variables,
    Michael> in order to know when this compatibility hack can be removed.

Tino, would it be possible to add text back in the manual saying what
the default values of these new variables are? People reading it
inside Emacs can obviously just inspect their values, but not everyone
reads inside Emacs.

Robert