Nixify simple_vim idea

I previously had an alias defined as `simple_vim`, which would start an instance
of Vim with a bare bones config. I had a to-do to Nixify it. That is
now (mostly) to-done.

When I try and install it with `nix-env -f ~/briefcase -iA tools.simple_vim`,
Nix fails and says that pkgs.stdenv is undefined. I will need to fix this one
day, but it is neither important nor urgent...

tools/simple_vim/config.vim

@@ -0,0 +1,98 @@
+" My barebones vimrc without any Vundle dependencies.
+"
+" I'm attempting to optimize the following:
+" - Minimize dependencies
+" - Maximize ergonomics
+" - Maximize Tmux compatibility
+" - Minimize shadowing of existing Vim KBDs
+"
+" Warning: This is currently unstable as it is a work-in-progress.
+"
+" Author: William Carroll <wpcarro@gmail.com>
+
+" Use <Space> as the leader key.
+let mapleader = " "
+nnoremap <leader>ev :tabnew<CR>:edit ~/.vimrc<CR>
+nnoremap <leader>sv :source ~/.vimrc<CR>
+nnoremap <leader>w  :w<CR>
+nnoremap <leader>h  :help 
+
+" increment,decrement numbers
+nnoremap + <C-a>
+" TODO: Restore with better KBD
+" nnoremap - <C-x>
+
+" Visit the CWD
+nnoremap - :e .<CR>
+
+" Turn line numbers on.
+set number
+
+" Easily create vertical, horizontal window splits.
+nnoremap sh :vsplit<CR>
+nnoremap sj :split<CR>:wincmd j<CR>
+nnoremap sk :split<CR>
+nnoremap sl :vsplit<CR>:wincmd l<CR>
+
+" Move across window splits.
+" TODO: Change to <M-{h,j,k,l}>.
+nnoremap <C-h> :wincmd h<CR>
+nnoremap <C-j> :wincmd j<CR>
+nnoremap <C-k> :wincmd k<CR>
+nnoremap <C-l> :wincmd l<CR>
+
+" TODO: Support these.
+" nnoremap <M-q> :q<CR>
+" nnoremap <M-h> :wincmd h<CR>
+" nnoremap <M-j> :wincmd j<CR>
+" nnoremap <M-k> :wincmd k<CR>
+" nnoremap <M-l> :wincmd l<CR>
+
+" Use <Enter> instead of G to support:
+"        20<Enter> - to jump to line 20
+"       d20<Enter> - to delete from the current line until line 20
+"   <C-v>20<Enter> - to select from the current line until line 20
+nnoremap <Enter> G
+onoremap <Enter> G
+vnoremap <Enter> G
+
+" Easily change modes on keyboards that don't have CapsLock mapped to <Esc>
+inoremap jk      <ESC>
+
+" CRUD tabs.
+nnoremap <TAB>   :tabnext<CR>
+nnoremap <S-TAB> :tabprevious<CR>
+nnoremap <C-t>   :tabnew<CR>:edit .<CR>
+nnoremap <C-w>   :tabclose<CR>
+" TODO: Re-enable these once <M-{h,j,k,l}> are supported.
+" nnoremap <C-l> :+tabmove<CR>
+" nnoremap <C-h> :-tabmove<CR>
+
+" Use H,L to goto beggining,end of a line.
+" Swaps the keys to ensure original functionality of H,L are preserved.
+nnoremap H ^
+nnoremap L $
+nnoremap ^ H
+nnoremap $ L
+
+" Use H,L in visual mode too
+vnoremap H ^
+vnoremap L $
+vnoremap ^ H
+vnoremap $ L
+
+" Emacs hybrid mode
+" TODO: model this after tpope's rsi.vim (Readline-style insertion)
+cnoremap <C-g> <C-c>
+cnoremap <C-a> <C-b>
+inoremap <C-a> <C-o>^
+inoremap <C-e> <C-o>$
+inoremap <C-b> <C-o>h
+inoremap <C-f> <C-o>l
+
+" Indenting
+" The following three settings are based on option 2 of `:help tabstop`
+set tabstop=4
+set shiftwidth=4
+set expandtab
+set autoindent

tools/simple_vim/default.nix

@@ -0,0 +1,10 @@
+{ pkgs ? import <nixpkgs> {}, ... }:
+
+let
+  script = pkgs.writeShellScriptBin "simple_vim" ''
+    ${pkgs.vim}/bin/vim -u ${./config.vim}
+  '';
+in pkgs.stdenv.mkDerivation {
+  name = "simple_vim";
+  buildInputs = [ script ];
+}