Re: Add function eshell/clear to clear current eshell buffer

[Eli Zaretskii <eliz@gnu.org>]

> From: Ted Zlatanov <tzz@lifelogs.com>
> Date: Sat, 18 Apr 2015 09:31:35 -0400
> 
> >> But eshell is not a terminal emulator.  It's a shell.  Emacs provides
> >> the text UI around it.
> 
> EZ> I don't see the significance of this observation for the issue at
> EZ> hand.  Eshell is an implementation of a shell in Emacs Lisp, and as
> EZ> such, Emacs is part of it.  Therefore, we should compare what Eshell's
> EZ> command do with what shells+emulators do.
> 
> I think Emacs' concepts of windows and buffers should override the
> typical terminal emulators' concepts of window and scrollback buffer.

Not when we are talking about a shell.

> Since Emacs typically doesn't clear just the window in normal usage,
> it's strange to do it here (especially by inserting blank lines).

It's a command; if you don't like it, don't use it.

But people who do want to start with a "clean slate" should be able
to.

> >> I would rename `eshell/clear' to `eshell/clear-view' and also provide
> >> `eshell/clear-buffer', if that's OK with Vibhav and everyone else?
> 
> EZ> Eshell should have commands named like corresponding shell commands.
> EZ> Having commands with no namesakes in popular shells makes very little
> EZ> sense to me.
> 
> >From the man page:
> 
>       clear clears your screen if this is possible, including its
>       scrollback buffer (if the extended "E3" capability is defined).
>       clear looks in the environment for the terminal type and then in
>       the terminfo database to determine how to clear the screen.
> 
> So, unless we come up with some E3 equivalent, I think it should be two
> commands or in some other way apparent that there's two operation modes
> to the `clear' eshell command.

The idea was that cleaning the scrollback buffer make little sense in
Emacs, because you gain nothing, but lose a chance to change your mind
later.  So I think inventing the equivalent of E3 would be wasted
effort.

> For simplicity, how about `eshell/clear' for the window and
> `eshell/clear-scrollback' for the whole buffer (also invoked with
> universal-prefix on `eshell/clear')? The scrollback clear should IMO
> also make sure undo is enabled, but the text is not in any registers.

I'm not necessarily object, but again: what would be the purpose of
removing the scrollback? what will that give you?