Continuous Integration Server in < 20 Lines

app.rb

require 'rubygems'
require 'sinatra'
require 'json'
require 'logger'

before do
  #only allow access to GitHub.
  ips = ['207.97.227.253', '50.57.128.197', '108.171.174.178'];
  halt 404, "D:<" unless ips.find_index(@env['REMOTE_ADDR'])>=0
end

post '/post-receive' do
  branch = JSON.parse(params[:payload])['ref'].split('/').pop
  log = Logger.new('log.txt').info(`./update_branch.sh #{branch}`)
end

update_branch.sh

#!/usr/bin/env bash 
echo updating branch $1...
cd /srv/mysite.com/$1/application
git pull
touch tmp/restart.txt