bug#13649: boobytrapped dired-do-async-shell-command question

[Juri Linkov]

>>> A command is running in the default buffer.  Use a new buffer? (yes or no)
>>> Which is a boobytrapped question, as picking "no" will always end up
>>> in failure...
>> Ah, to you "no" means "don't use a new buffer"?  Yes, this is too ambiguous.
>> A better question would be:
>
>>   A command is running in the default buffer.  Run in a new buffer?
>>     (yes or no)
>
> I think it's got the same problem.  I think the question should be more
> something like:
>
>   A command is running in the default buffer.  Kill it or use a new buffer?
>
> with C-g being the answer for "don't use a new buffer and don't kill it".

Alas, this means there is no more "yes/no" question.  Of course,
it could be split to two "yes/no" questions like `find-alternate-file'
used to do until the recent changes that now asks only one question
(yes-or-no-p "Kill and replace the buffer without saving it? ")
I see no way to do the same for the async-shell-command default question.

There is a separate option in `async-shell-command' that asks that question
"A command is running in the default buffer.  Kill it? ".  If is also
possible to combine all other options into one question like:

  A command is running in the default buffer.  What to do? (k/c/r/h)

where the key `k' would mean to kill the running process, `c' - create
a new buffer, `r' - rename the buffer with the running process, and
`h' - help with the explanation of these options.