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Re: Browsing the history of commands. Inconsistency between Bash and Ema

From: Bob Proulx
Subject: Re: Browsing the history of commands. Inconsistency between Bash and Emacs
Date: Thu, 13 Feb 2014 15:32:26 -0700
User-agent: Mutt/1.5.21 (2010-09-15)

Dani Moncayo wrote:
> Emacs uses M-p/M-n to browse the minibuffer history (and C-p/C-n to
> move to the previous/next line in a multi-line buffer), whereas Bash
> uses C-n/C-p for browsing the command history (and doesn't use M-p/M-n
> for anything, AFAIK).
> It would be nice to remove this inconsistency (this is the obvious
> part), and IMO TRT would be to make Bash behave like Emacs, that is:
> 1. Use M-p/M-n to browse the command history (instead of the current C-p/C-n).
> 2. Use C-p/C-n to move to the previous/next line, in the current
> command being edited.

This is completely putting the cart before the horse.  And going down
that road creates a circular line of reasoning which has no end to the
loop cycle.  Plus it is a radical change in fundamental behavior.
Please don't.

The entire reason that bash's readline emacs mode uses C-n and C-p is
that those are the emacs keys for next-line and previous-line.  If
emacs were using M-p and M-n for previous and next then bash would
have done so too.  Bash didn't make this up.  It is using the keys
from emacs for emacs mode and those keys are C-n and C-p.  Editing the
history is just like editing a file.  C-p takes you to the previous
line.  C-n takes you to the next line.

Now enter emacs.  I mean literally.  (I have been using emacs for a
very long time by the way.  I am using it now.)  Emacs has the feature
including of being able to edit the minibuffer and also being able to
run an inferior shell process in a buffer.  Both are very similar
cases and should be discussed together.  In those buffers if you want
to go to the previous line or the next line then what keys do you use?
You use C-p and C-n to go to the previous line or the next line.

But that is not editing the history.  That is editing the buffer.
There the previous and next lines are parts of the visible screen.  It
isn't a history of the screen.  For using bash in an inferior shell if
you want to recall shell history you can't use C-p and C-n because
those are shadowed by the emacs layer of keybindings that move
previous and next lines.  Therefore M-p and M-n were the natural
second choice to navigate by adding another mental layer of
navigation.  (Although emacs itself is keeping the input history.)
Same thing for the minibuffer.

So now people say, I am now used to using M-p and M-n in emacs to
avoid the C-p/C-n.  Let's set that up for bash.  (Of course you can
easily do this if you desire.  Just do it.  Several people suggested
it.)  Well, let's say for discussion that you get used to that
setting.  The entire argument so far is that people are "used to it".

Now people become used to navigating the previous line with M-p and
the next line with M-n in bash.  Now they go to emacs.  What do they
do there?  They find that in emacs M-p and M-n *do not navigate* the
previous line and next line.  They find that bash and emacs are once
again inconsistent!

In that future time let me file a bug with emacs asking for them to
change their previous-line and next-line key bindings to be compatible
with the new bash bindings of M-p and M-n for previous and next line.
Why?  Because they are "used to it".  That request is just as valid as
this request to do so with bash.  So why not?  Why wouldn't emacs
change M-p and M-n to be previous line and next line?  Let's say they
do for continued discussion.

Now in the future, future time where emacs has now adopted M-p and M-n
for previous and next line.  Now they need a way to escape the emacs
layer again but with the new set of keys.  In emacs I really don't
want to need to use C-c as a prefix key for the minibuffer and the
inferior shell buffer like in term mode.  But let's say they do.
Would there then be a request for bash to set up C-c M-n and C-c M-p
for next and previous line?  I think there would be and it would just
be an endless cycle.

As Chet said the mental model of what is happening at those two points
of action in each program is different.


P.S. This is going to be a rant and run because I am offline for
several days after this.

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