Github post-receive hook for auto-deployment of a Web site document root

github-autodeploy.rb

require "rubygems"
require "sinatra"
require "json"

# Configure this with the directory path for the Web server's clone of the Git repo
git_dir = '/var/www/origin.git'

# Configure the mappings between Git branches and Web document roots
branch_to_working_directory = {
  'www'     => '/var/www/www.example.com',
  'staging' => '/var/www/staging.example.com/',
  'dev'     => '/var/www/dev.example.com/'
}

post '/' do
  push = JSON.parse(params[:payload])
  ref = push['ref'] || raise("ref required in payload")
  branch = ref.match(/([^\/]+)$/)[0]
  work_dir = branch_to_working_directory[branch]
  warn "Got Github hook for ref #{ref}, branch #{branch}, work_dir #{work_dir}"
  
  system "git --git-dir=#{git_dir} --work-tree=#{work_dir} add ."
  system "git --git-dir=#{git_dir} --work-tree=#{work_dir} fetch"
  system "git --git-dir=#{git_dir} --work-tree=#{work_dir} reset --hard -q origin/#{branch}"
  ''
end