docs, refactor: update to new aucmd API

• remove vim source code for implementing tidy's autocommands
      and instead use the Lua API from 0.7

    • update README with improved explanation and new installation
      instructions

    Resolves #4

README.md

@@ -11,27 +11,22 @@ on every `BufWritePre`.
 ![tidy](https://user-images.githubusercontent.com/59481467/170846833-40ab4e8c-ebdf-42c4-b1f1-a4d874f27ea8.gif)
 
 
-**Notes**: See the `cfg` branch for increased functionality and configuration.
-
-
 ## About
-I wrote this as a wrapper around a few vim regex commands used for formatting files before I began using formatters. These commands are not mine, see the `Credits` section below for sources. My contribution is a basic conditional which protects the user from an error when the cursor is in the group of empty lines removed from the end of the buffer. Even with real formatters in my setup now I still like and use this because I like these specific formats to be applied to every buffer and don't want to have a formatting tool installed for them. There really isn't a reason to have this in a plugin other than wanting to disseminate this for new users and people who didn't know you could do this. You could (should) instead just yank and put the code right in your config.
+I originally wrote this as a wrapper around a couple of vim regex commands used for formatting files before I began using formatters. These commands are not mine, please see the `Credits` section below for sources. My contribution is a basic conditional which ensures that the user's cursor doesn't migrate during the cleaning operations conducted on the buffer's contents unless the cursor is in the removed white space. Even with real formatters in my setup now, I still like and use this because I like these specific formats to be applied to every buffer and don't want to have a formatting tool installed for them. There really isn't a reason to have this in a plugin other than wanting to disseminate it for new users or people who didn't know you could do this. You could (should) instead just yank and put the code right in your configuration.
 
 
 ## Installation
 - Packer
 
 ```lua
-use "mcauley-penney/tidy.nvim"
+use({
+    "mcauley-penney/tidy.nvim",
+    config = function()
+        require("tidy").setup()
+    end
+})
 ```
 
-or with lazy-loading
-
-```lua
-use{ "mcauley-penney/tidy.nvim", event = "BufWritePre" }
-```
-
-
 ## Credits
 - [Vim Tips Wiki entry for removing unwanted spaces](https://vim.fandom.com/wiki/Remove_unwanted_spaces#Automatically_removing_all_trailing_whitespace)
 
@@ -40,7 +35,3 @@ use{ "mcauley-penney/tidy.nvim", event = "BufWritePre" }
 - [This line](https://github.com/gpanders/editorconfig.nvim/blob/ae3586771996b2fb1662eb0c17f5d1f4f5759bb7/lua/editorconfig.lua#L180)
 in [gpanders/editorconfig.nvim](https://github.com/gpanders/editorconfig.nvim) for exposing me to the `keepjumps`
 and `keeppatterns` modifiers
-
-
-## Todo
-- [ ] preserve undotree 

lua/tidy/init.lua

@@ -1,17 +1,20 @@
 local M = {}
 
-function M.tidy_up()
-    -- get tuple of cursor position before making changes
+function M.setup()
+    local tidy_grp = vim.api.nvim_create_augroup("tidy", { clear = true })
+
+    vim.api.nvim_create_autocmd("BufWritePre", {
+        group = tidy_grp,
+        callback = function()
             local pos = vim.api.nvim_win_get_cursor(0)
 
-    -- delete all whitespace, see source 1
             vim.cmd([[:keepjumps keeppatterns %s/\s\+$//e]])
 
             -- delete all lines at end of buffer, see source 2
             vim.cmd([[:keepjumps keeppatterns silent! 0;/^\%(\n*.\)\@!/,$d]])
 
             -- get row count after line deletion
-    local end_row = vim.api.nvim_buf_line_count(0)
+            local last_row = vim.api.nvim_buf_line_count(0)
 
             --[[
                 if the row value in the original cursor
@@ -20,13 +23,15 @@ function M.tidy_up()
                 (meaning that the cursor was inside of
                 the group of empty lines at the end of
                 the file when they were deleted), set
-        the cursor row to the last line
+                the cursor row to the last line.
             ]]
-    if pos[1] > end_row then
-        pos[1] = end_row
+            if pos[1] > last_row then
+                pos[1] = last_row
             end
 
             vim.api.nvim_win_set_cursor(0, pos)
+        end,
+    })
 end
 
 return M

plugin/tidy.vim

@@ -1,4 +0,0 @@
-augroup Tidy
-    au!
-    au BufWritePre * lua require( "tidy" ).tidy_up()
-augroup END