bug#39627: [PATCH] Skip shell prompt on current line even if it's protected

[Eli Zaretskii]

> From: Steven Allen <steven@stebalien.com>
> Date: Sat, 15 Feb 2020 15:13:59 -0800
> 
> * lisp/eshell/em-prompt.el (eshell-previous-prompt): Really go to the
> beginning of the line, even if it's protected.
> 
> When the eshell prompt is protected (e.g., with rear non-sticky,
> inhibited movements, etc.), `beginning-of-line' won't move to the
> actual beginning of the line and therefore won't skip over the
> prompt.  This change simply switches to (forward-line 0).

Thanks, pushed to the emacs-27 branch.

Please note that I needed to massage your log message a little, to
make it more according to our conventions (described in CONTRIBUTE).
Please study the changes I made and try to follow this style in the
future.