mina rollback from https://github.com/mina-deploy/mina/issues/9#issuecomment-37499645

mina-rollback.rb

desc "Rolls back the latest release"
task :rollback => :environment do
  queue! %[echo "-----> Rolling back to previous release for instance: #{domain}"]

  # Delete existing sym link and create a new symlink pointing to the previous release
  queue %[echo -n "-----> Creating new symlink from the previous release: "]
  queue %[ls "#{deploy_to}/releases" -Art | sort | tail -n 2 | head -n 1]
  queue! %[ls -Art "#{deploy_to}/releases" | sort | tail -n 2 | head -n 1 | xargs -I active ln -nfs "#{deploy_to}/releases/active" "#{deploy_to}/current"]

  # Remove latest release folder (active release)
  queue %[echo -n "-----> Deleting active release: "]
  queue %[ls "#{deploy_to}/releases" -Art | sort | tail -n 1]
  queue! %[ls "#{deploy_to}/releases" -Art | sort | tail -n 1 | xargs -I active rm -rf "#{deploy_to}/releases/active"]
end