bug#65604: [PATCH] Display the exit code if the last command failed in Eshell

[Eli Zaretskii]

> Cc: 65604@debbugs.gnu.org, jporterbugs@gmail.com, dm@mssdvd.com
> Date: Wed, 30 Aug 2023 19:45:29 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> Always try to avoid possible confusion due to wrong attribution (does
> "it's" refer to the mode line or to the last command or to the exit
> code?).  So:
> 
>   If a command exits abnormally, Eshel now displays its exit code on
>   the mode line.

Even better:

  If a command exits abnormally, Eshel now displays the command's exit
  code on the mode line.