bug#25665: 26.0.50; [PATCH] Indicate prefix arg in minibuffer prompt for shell-command

[npostavs]

Tino Calancha <tino.calancha@gmail.com> writes:

> On Thu, 9 Feb 2017, npostavs@users.sourceforge.net wrote:
>
>> On Thu, Feb 9, 2017 at 11:53 AM, Tino Calancha <tino.calancha@gmail.com> 
>> wrote:
>>
>>> The meaning of the prefix argument must be explained in the docstring.
>>> That and the manual are the source of documentation, not the prompt.
>>
>> But it's nice if Emacs gives you a different prompt, so that you can be
>> sure you typed in the command correctly.
> Confirmation for having typed C-u?
> Well, sometimes some keys in old keyboards die... ;-)

We already have that in `echo-keystrokes'.

But I'm thinking also of times when you do C-u M-! and then switch to
another window to copy the command, then maybe when you come back, you
don't remember 100% what you were doing.

>> Just like M-& gives a
>> different prompt from M-!, even though you could figure out the
>> different meaning just by reading the docstring of each command.
> These are different commands so its Emacs (and whatever editor)
> convention to how a different prompt.  The OP suggests to use
> a different prompt for the same command w/ or w/o prefix.

M-& and M-! are practically the same command anyway, async-shell-command
is basically just

    (defun async-shell-command (command)
      (shell-command (concat command "&")))

>
> There are lots of commands in Emacs accepting a raw,
> numeric prefix etc.  If we change M-! prompt, we might
> also want to tune the prompt for all of them.  Do we want that?

IMO yes, if the difference can be summarized in the prompt concisely
enough.