bug#30280: async-shell-command-display-buffer doesn't work anymore

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Date: Mon, 29 Jan 2018 00:20:30 +0200
> 
> 0. emacs -Q
> 1. Eval: (setq async-shell-command-buffer 'new-buffer
>                async-shell-command-display-buffer nil)
> 2. M-& sleep 3600
> 3. M-& sleep 3; echo "xyzzy"
> 
> At the step 2 “*Async Shell Command*” is not shown because of no output,
> this is ok.
> 
> But at the step 3 “*Async Shell Command*<2>” is not shown after 3 seconds
> when the output arrives, this is a regression.
> 
> It seems it is caused by commit#9f4f130 from bug#28997
> 
> PS: Also it doesn't work with less official configuration:
> 0. emacs -Q
> 1. Eval: (setq async-shell-command-display-buffer nil)
>          (add-hook 'shell-mode-hook 'rename-uniquely)
> 2. M-& sleep 3600
> 3. M-& sleep 3; echo "xyzzy"

Thanks for reporting this.  Basil, can you take a look, please?

P.S. Juri, in the future, could you please make sure the version of
Emacs where you discovered this appears in the bug report, either in
the Subject or in the body?