bug#72018: 30.0.60; [PATCH] Don't emit a prompt when a background Eshell process is killed

[Eli Zaretskii]

> Date: Tue, 9 Jul 2024 11:04:05 -0700
> From: Jim Porter <jporterbugs@gmail.com>
> 
> This is a regression from Emacs 29, likely due to some changes I made to 
> improve support for complex background commands. Eli, is this ok to 
> merge to the release branch?

I don't think I understand the essence of the change, and thus cannot
appreciate its effects enough to be able to answer this.  What is the
significance of '(car command)' in this hunk:

> +          ;; Reset the prompt if the command we just aborted was in the
> +          ;; foreground.
> +          (unless (car command)
> +            (declare-function eshell-reset "esh-mode" (&optional no-hooks))
> +            (eshell-reset)))))))

IOW, why '(car command)' is used as an indication of a fore/background
command?  Also, why does the comment say "foreground" while your text
says we don't want the prompt if the killed program was in the
background?