vi-mode: Adding additional C-w functionality (Window management)

[LeeLaffan]

Preface

Hi! I just want to start off by saying how much I am enjoying Lem. It has been great to work with the project.
I am a vim user, and wanted to add some of the functionality around window management to the Lem vi-mode.

This is my first public pull request, so please let me know if anything is not protocol. I am also new to common lisp and lisp in general, so I am very happy to take on feedback about the code. Same with the Lem specific stuff. I am not an expert yet.

I would also be happy to break this up into smaller pull requests if that would help, let me know. Although there are sections like Keybinds and Ex-Commands, they use the same vi-* functions in a lot of cases.

Thank you for your time.
Lee

Feature Breakdown

I tested what I could with a clean vim build to verify this functionality matched.
To each key where the docs specified(https://vimhelp.org/windows.txt.html), I added the alternative C-w h & C-w C-h. Some are not in vim like C-w C-c.

Keybinds

C-w hjkl

Navigating splits.
To allow number prefix, eg. 2 C-w l

New Commands

   (vi-window-move-left)
   (vi-window-move-down)
   (vi-window-move-up)
   (vi-window-move-right)

C-w s/v

Splits the window and moves to the split.
This now allows a number prefix, eg. 3 C-w v

New Commands

  (vi-window-split-horizontally)
  (vi-window-split-vertically)

C-w n

Split the window and creates a new window as per the vim docs here: https://vimhelp.org/windows.txt.html#opening-window

New Commands

  (vi-window-split-vertically-new)

C-w c

Closes the current split. If there is one window, don't close it as in vi/vim.

New Commands

  (vi-close)

C-w p

Uses Lem function to go to previous window.

  (define-key *motion-keymap* "C-w p" 'previous-window)

C-w o

Uses Lem function to delete other windows.

  (define-key *motion-keymap* "C-w o" 'delete-other-windows)

Ex-Commands

These link up with the above keybinds for the most part.

:new

Creates a new buffer in a split below. Uses the C-w n command: (vi-window-split-vertically-new)

:vne(w)

Creates a new buffer in a split to the right. Uses something similar to the above: (vi-window-split-horizontally-new)
There isn't a vanilla vim keybinding to match this functionality.

:enew(w)

Opens the specified file name or creates a blank buffer.
There isn't a vanilla vim keybinding to match this functionality.

:clo(se)

Closes the buffer, unless it's the last one. Uses the C-w c command: (vi-close)

:on(ly)

Uses Lem function to delete other windows. Same as C-w o: (lem:delete-other-windows)

Bug with :wa

There was a small bug in the matching for :wa(ll) and :wa(ll)!
They did not treat the (ll) as optional.

  ^wa(?:ll)$ 

  should be:

  ^wa(?:ll)?$

[cxxxr]

Thanks a lot!

[LeeLaffan]

Seems I used a variable that is marked as ignored. This is cleaned up in this PR:

#1714