Capistrano::Configuration.instance.load do 
  namespace :deploy do 
    desc "Save the current source code revision to version.rb" 
    task :save_version_number, :roles => :app do 
      run "echo APP_VERSION='#{source.latest_revision}' > 
#{release_path}/lib/app_version.rb" 
    end 

    after :update_code, :save_version_number 
  end 
end