Don't use autocmd Lua API on older versions of Nvim

It's easy enough to support old versions. Supporting the version
supported by the oldest Ubuntu LTS seems reasonable.

Fixes: #28

after/plugin/editorconfig.vim

@@ -0,0 +1,26 @@
+" Copyright 2022 Gregory Anders
+"
+" SPDX-License-Identifier: GPL-3.0-or-later
+"
+" This program is free software: you can redistribute it and/or modify it under
+" the terms of the GNU General Public License as published by the Free Software
+" Foundation, either version 3 of the License, or (at your option) any later
+" version.
+"
+" This program is distributed in the hope that it will be useful, but WITHOUT
+" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+" FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+" details.
+"
+" You should have received a copy of the GNU General Public License along with
+" this program. If not, see <https://www.gnu.org/licenses/>.
+
+if exists('g:loaded_editorconfig')
+ finish
+endif
+let g:loaded_editorconfig = 1
+
+augroup editorconfig
+ autocmd!
+ autocmd BufNewFile,BufRead,BufFilePost * lua require('editorconfig').config(tonumber(vim.fn.expand('<abuf>')))
+augroup END

fnl/editorconfig.fnl

@@ -79,9 +79,12 @@
 (fn properties.trim_trailing_whitespace [bufnr val]
  (assert (or (= val :true) (= val :false)) "trim_trailing_whitespace must be either 'true' or 'false'")
  (when (= val :true)
- (vim.api.nvim_create_autocmd :BufWritePre {:group :editorconfig
- :buffer bufnr
- :callback trim-trailing-whitespace})))
+ (if (= (vim.fn.has :nvim-0.7) 1)
+ (vim.api.nvim_create_autocmd :BufWritePre {:group :editorconfig
+ :buffer bufnr
+ :callback trim-trailing-whitespace})
+ (vim.cmd (: "autocmd editorconfig BufWritePre <buffer=%d> lua require('editorconfig').trim_trailing_whitespace()"
+ :format bufnr)))))
 
 (fn properties.insert_final_newline [bufnr val]
  (assert (or (= val :true) (= val :false)) "insert_final_newline must be either 'true' or 'false'")
@@ -165,8 +168,9 @@
  (tset vim.b bufnr :editorconfig applied))))
 
 (fn trim_trailing_whitespace []
- (vim.notify_once (debug.traceback "editorconfig.nvim: trim_trailing_whitespace() is deprecated and will soon be removed" 2)
- vim.log.levels.WARN)
+ (when (= (vim.fn.has :nvim-0.7) 1)
+ (vim.notify_once (debug.traceback "editorconfig.nvim: trim_trailing_whitespace() is deprecated and will soon be removed" 2)
+ vim.log.levels.WARN))
  (trim-trailing-whitespace))
 
 {: config