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

[Juri Linkov]

>> Typing C-h in the minibuffer is useful for other things,
>> e.g. to see available keybindings with `C-h b', `C-h m'.
>> Maybe then `?' would be appropriate as a short key?
>
> It hadn't occurred to me that somebody would want to say `C-h b' in a
> yes-or-no-prompt, but I guess it's possible?  On the other hand, I think
> there's an advantage to having the same help key in both y-or-n-p and
> yes-or-no-p.

Actually, `C-h' is useful in `y-or-n-p' as well for the same reasons.
For example, `C-h b' in a `y-or-n-p' prompt shows:

  Key             Binding
  y               act
  n               skip
  C-l             recenter
  ...

BTW, (info "(emacs) Yes or No Prompts") says:

     With both types of yes-or-no query the minibuffer behaves as
  described in the previous sections; you can recenter the selected window
  with ‘C-l’, scroll that window (‘C-v’ or ‘PageDown’ scrolls forward,
  ‘M-v’ or ‘PageUp’ scrolls backward)

But in fact ‘C-l’ doesn't scroll the window, ‘C-v’ and ‘PageDown’ don't
scroll forward, and ‘M-v’ and ‘PageUp’ don't scroll backward.  Should they?