bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

[Eli Zaretskii <eliz@gnu.org>]

> From: Reza Shafiei <joghd1988@outlook.com>
> Date: Fri, 27 Jan 2023 15:16:01 +0000
> msip_labels: 
> 
> I apologize in advance for any mistakes since English is not my native
> language and it is the first time that I report a bug.
> 
> How to reproduce:
> 1) emacs -Q
> 2) (setq shell-command-dont-erase-buffer t)
> 3) M-! with some command that generates short output, like
>    M-! echo "foo".  Output is displayed in the minibuffer:
>    ----------------
>    foo
>    ----------------
> 4) M-! with another command that also generates short output,
>    like M-! echo "bar".  You will see that the output of previous
>    commands is also displayed again in the minibuffer:
>    ----------------
>    foo
>    bar
>    ----------------
> 
> `shell-command-on-region' has the same behavior.
> 
> What I understand form the documentation of these two commands is
> that only the output of the most recent command should be
> displayed in the minibuffer (if it is short of course), not the
> entire content of *Shell Command Output*.

Thanks.

The documentation describes the default situation, where
shell-command-dont-erase-buffer is not customized.

I've now updated the documentation to describe this effect of
customizing that variable.  I think this fixes the discrepancy.