bug#30213: 26.0.91; shell buffer not displayed when not erased and async-shell-command-display-buffer is used

[Eli Zaretskii <eliz@gnu.org>]

> From: "Basil L. Contovounesios" <contovob@tcd.ie>
> Date: Tue, 23 Jan 2018 18:53:13 +0000
> Cc: 30213@debbugs.gnu.org
> 
> * lisp/simple.el (shell-command): Display async command buffer on
> process output for every invocation, not just the first. (bug#30213)
> ---
>  lisp/simple.el | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/lisp/simple.el b/lisp/simple.el
> index 3ac6b86381..20e22bf98f 100644
> --- a/lisp/simple.el
> +++ b/lisp/simple.el
> @@ -3551,9 +3551,7 @@ shell-command
>                      (add-function :before (process-filter proc)
>                                    (lambda (process _string)
>                                      (let ((buf (process-buffer process)))
> -                                      (when (and (zerop (buffer-size buf))
> -                                                 (string= (buffer-name buf)
> -                                                          bname))
> +                                      (when (string= (buffer-name buf) bname)
>                                          (display-buffer buf))))))))
>  	    ;; Otherwise, command is executed synchronously.
>  	    (shell-command-on-region (point) (point) command

Looks like you are removing the feature we just introduced in Emacs
26, see commit 85512e7: it shows the shell buffer only if there is
some output there.  Or am I missing something?