module: allow require('.')

Previously, the minimal argument to require the current directory was
require('./'). This commits allows to skip the trailing slash.

Fixes: nodejs#1178
PR-URL: nodejs#1185
Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>
Reviewed-By: Christian Tellnes <christian@tellnes.no>
Reviewed-By: Roman Reiss <me@silverwind.io>

lib/module.js

@@ -205,7 +205,7 @@ Module._resolveLookupPaths = function(request, parent) {
   }
 
   var start = request.substring(0, 2);
-  if (start !== './' && start !== '..') {
+  if (start !== '.' && start !== './' && start !== '..') {
     var paths = modulePaths;
     if (parent) {
       if (!parent.paths) parent.paths = [];

test/fixtures/module-require/relative/dot-slash.js

@@ -0,0 +1 @@
+module.exports = require('./');

test/fixtures/module-require/relative/dot.js

@@ -0,0 +1 @@
+module.exports = require('.');

test/fixtures/module-require/relative/index.js

@@ -0,0 +1 @@
+exports.value = 42;

test/parallel/test-require-extensions-main.js

@@ -2,3 +2,9 @@ var common = require('../common');
 var assert = require('assert');
 
 require(common.fixturesDir + '/require-bin/bin/req.js');
+
+var a = require(common.fixturesDir + '/module-require/relative/dot.js');
+var b = require(common.fixturesDir + '/module-require/relative/dot-slash.js');
+
+assert.equal(a.value, 42);
+assert.equal(a, b, 'require(".") should resolve like require("./")');