Guardfile

guard 'rails', :port => 3000, :server => :thin, :debugger => true do
  watch('Gemfile.lock')
  watch(%r{^(config|lib)/.*})

  # When caching classes, also restart when app is changed
  cache_line = `cat config/environments/development.rb | grep "config\.cache_classes ="`
  if cache_line =~ /=\s*(true|false)/ && $1 == 'true'
    watch(%r{^app/.*})
  end
end