Add @lewis6991's improvement for lazy-load command completions

lua/packer/compile.lua

@@ -570,19 +570,20 @@ local function make_loaders(_, plugins, output_lua, should_profile)
   for command, names in pairs(commands) do
     local command_line
     if string.match(command, '^%w+$') then
-      -- Better command completions here are due to @folke
+      -- Better command completions here are due to @folke and @lewis6991
       command_line = fmt(
         [[pcall(vim.api.nvim_create_user_command, '%s', function(cmdargs)
           require('packer.load')({%s}, { cmd = '%s', l1 = cmdargs.line1, l2 = cmdargs.line2, bang = cmdargs.bang, args = cmdargs.args, mods = cmdargs.mods }, _G.packer_plugins)
         end,
         {nargs = '*', range = true, bang = true, complete = function()
           require('packer.load')({%s}, { cmd = '%s' }, _G.packer_plugins)
-          vim.api.nvim_input('<space><bs><tab>')
+          return vim.fn.getcompletion('%s ', 'cmdline')
       end})]],
         command,
         table.concat(names, ', '),
         command,
         table.concat(names, ', '),
+        command,
         command
       )
     else