Node.js + express: specify routes - node.js

Question

In my understanding, the way to serve views is to do the following:
app.set('view engine', 'ejs'); // or jade or whatever
app.set('views', __dirname + '/views'); // specify where to find the view files e.g. index.ejs
app.get("/", function(req, res) { res.render('index') });
However, when I check the code here https://github.com/jedireza/drywall/ , which is a boilerplate for node user management, I don't see any routes defined in app.js. But it works fine and if I type the url /signup in browser it will render signup.jade.
Which part, or which middleware is doing the magic of routing?
app.js content:
'use strict';
//dependencies
var config = require('./config'),
express = require('express'),
cookieParser = require('cookie-parser'),
bodyParser = require('body-parser'),
session = require('express-session'),
mongoStore = require('connect-mongo')(session),
http = require('http'),
path = require('path'),
passport = require('passport'),
mongoose = require('mongoose'),
helmet = require('helmet'),
csrf = require('csurf');
//create express app
var app = express();
//keep reference to config
app.config = config;
//setup the web server
app.server = http.createServer(app);
//setup mongoose
app.db = mongoose.createConnection(config.mongodb.uri);
app.db.on('error', console.error.bind(console, 'mongoose connection error: '));
app.db.once('open', function () {
//and... we have a data store
});
//config data models
require('./models')(app, mongoose);
//settings
app.disable('x-powered-by');
app.set('port', config.port);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
//middleware
app.use(require('morgan')('dev'));
app.use(require('compression')());
app.use(require('serve-static')(path.join(__dirname, 'public')));
app.use(require('method-override')());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser(config.cryptoKey));
app.use(session({
resave: true,
saveUninitialized: true,
secret: config.cryptoKey,
store: new mongoStore({ url: config.mongodb.uri })
}));
app.use(passport.initialize());
app.use(passport.session());
app.use(csrf({ cookie: { signed: true } }));
helmet(app);
//response locals
app.use(function(req, res, next) {
res.cookie('_csrfToken', req.csrfToken());
res.locals.user = {};
res.locals.user.defaultReturnUrl = req.user && req.user.defaultReturnUrl();
res.locals.user.username = req.user && req.user.username;
next();
});
//global locals
app.locals.projectName = app.config.projectName;
app.locals.copyrightYear = new Date().getFullYear();
app.locals.copyrightName = app.config.companyName;
app.locals.cacheBreaker = 'br34k-01';
//setup passport
require('./passport')(app, passport);
//setup routes
require('./routes')(app, passport);
//custom (friendly) error handler
app.use(require('./views/http/index').http500);
//setup utilities
app.utility = {};
app.utility.sendmail = require('./util/sendmail');
app.utility.slugify = require('./util/slugify');
app.utility.workflow = require('./util/workflow');
//listen up
app.server.listen(app.config.port, function(){
//and... we're live
});

Answer 1

The routes are being added here:
//setup routes
require('./routes')(app, passport);