bug#60666: 30.0.50; [PATCH] Use field properties in Eshell buffers

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 10 Jan 2023 11:28:17 -0800
> Cc: 60666@debbugs.gnu.org
> From: Jim Porter <jporterbugs@gmail.com>
> 
> On 1/10/2023 4:13 AM, Eli Zaretskii wrote:
> > I don't think I understand why keeping eshell-bol and telling people
> > to bind <HOME> to that function if they want wouldn't be a much more
> > reasonable solution.  I'm probably missing something.
> 
> Do you mean that users who want <home> to go to the very beginning of 
> the line would bind it to 'eshell-bol'? If so, that wouldn't help. 
> 'eshell-bol' moves the point to the beginning of the user's input, not 
> the actual beginning of the line.

That's not what I see in Emacs 29.  C-a moves to the beginning of
input, i.e. it stops at the end of the prompt, whereas HOME goes all
the way to the beginning of screen line, including the prompt.

"C-h c" says that C-a is bound to eshell-bol, but HOME is bound to
move-beginning-of-line.

I'm asking why not let users have this distinction after your change,
with some easy customization?

> If you mean the other way, and that users who want <home> to go to the 
> beginning of the input should just bind it to 'eshell-bol', that would 
> help, but then we wouldn't get the benefits of using 'field' properties 
> in Eshell. One of the nice things about using 'field' properties is that 
> 'eshell-prompt-regexp' is no longer necessary[1]. That regexp is fairly 
> brittle. Also, users who customize their prompt need to make sure they 
> update it correctly.

I understand the benefits, but from user POV we just removed some
functionality as the price of making maintenance easier.  That is not
a good balance for users who want the removed functionality.