Enable opt in project configs

plugin/commands.lua

@@ -206,6 +206,34 @@ vim.api.nvim_create_user_command('DiagnosticToggle', function(_)
   vim.diagnostic.enable(not vim.diagnostic.is_enabled())
 end, {})
 
+-- :Exrc create a project-local .nvim.lua in the current directory which adds a
+-- local runtime directory to 'runtimepath', defaulting to .config/nvim. Bang to
+-- overwrite an existing file. The result is trusted so it is sourced on the next
+-- start, editing it revokes that and requires :trust again. See :h 'exrc'.
+vim.api.nvim_create_user_command('Exrc', function(opts)
+  local path = vim.fs.joinpath(vim.fn.getcwd(), '.nvim.lua')
+  if vim.uv.fs_stat(path) and not opts.bang then
+    vim.notify(path .. ' already exists, use :Exrc! to overwrite',
+      vim.log.levels.ERROR)
+    return
+  end
+  local dir = opts.args ~= '' and opts.args or '.config/nvim'
+  vim.fn.writefile({
+    "local root = vim.fs.dirname(debug.getinfo(1, 'S').source:gsub('^@', ''))",
+    "local dir = vim.fs.joinpath(root, '" .. dir .. "')",
+    '',
+    'vim.opt.runtimepath:prepend(dir)',
+    "vim.opt.runtimepath:append(vim.fs.joinpath(dir, 'after'))",
+    '',
+    "-- lazy.nvim unsets 'loadplugins' so source this dir's plugin/ files here",
+    "for _, file in ipairs(vim.fn.glob(dir .. '/plugin/**/*.lua', false, true)) do",
+    '  dofile(file)',
+    'end',
+  }, path)
+  vim.secure.trust({ action = 'allow', path = path })
+  vim.cmd.edit(path)
+end, { bang = true, nargs = '?', complete = 'dir' })
+
 -- :ResizeFixed acts like :resize but also fixes the window size so it stops
 -- automatically changing when other windows reflow. Respects the :vertical
 -- modifier, resizing and fixing the width instead of the height.