chore: simplify generate code (#189)

generate.js

@@ -76,20 +76,19 @@ function generate (dir, cb) {
 
 function cli (args) {
   const opts = argv(args)
+  const dir = opts._[0]
 
-  if (opts._[0] && existsSync(opts._[0])) {
-    if (opts._[0] !== '.' && opts._[0] !== './') {
+  if (dir && existsSync(dir)) {
+    if (dir !== '.' && dir !== './') {
       log('error', 'directory ' + opts._[0] + ' already exists')
       process.exit(1)
     }
   }
-  if (opts._[0] === undefined) {
+  if (dir === undefined) {
     log('error', 'must specify a directory to \'fastify generate\'')
     process.exit(1)
   }
 
-  const dir = opts._[0]
-
   if (existsSync(path.join(dir, 'package.json'))) {
     log('error', 'a package.json file already exists in target directory')
     process.exit(1)