Source packer automatically if not installed

lua/andrew/packer.lua

@@ -1,4 +1,15 @@
-vim.cmd.packadd("packer.nvim")
+local ensure_packer = function()
+  local fn = vim.fn
+  local install_path = fn.stdpath('data')..'/site/pack/packer/start/packer.nvim'
+  if fn.empty(fn.glob(install_path)) > 0 then
+    fn.system({'git', 'clone', '--depth', '1', 'https://github.com/wbthomason/packer.nvim', install_path})
+    vim.cmd [[packadd packer.nvim]]
+    return true
+  end
+  return false
+end
+
+local packer_bootstrap = ensure_packer()
 
 return require("packer").startup(function(use)
   use "wbthomason/packer.nvim"
@@ -117,5 +128,9 @@ return require("packer").startup(function(use)
     "glacambre/firenvim",
     run = function() vim.fn["firenvim#install"](0) end
   }
+
+  if packer_bootstrap then
+    require('packer').sync()
+  end
 end)