Capistrano deploy:setup task without root permission

deploy.rb

namespace :deploy do
  task :setup, :except => { :no_release => true } do
    dirs = [deploy_to, releases_path, shared_path]
    dirs += shared_children.map { |d| File.join(shared_path, d.split('/').last) }
    run "mkdir -p #{dirs.join(' ')}"
    run "chmod g+w #{dirs.join(' ')}" if fetch(:group_writable, true)
  end
end