gating-deploy.rb

namespace :deploy do

  namespace :gate do
    task :default do
      if "#{stage}" == "production"
        stg = CLI.ui.ask "Which environment are you deploying to again? "
        unless stg == "#{stage}"
          puts "I am not convinced, sorry."
          exit(1)
        end
      end
    end

    task :schema do
      migrations = `git diff --name-only #{current_revision}..#{branch} db/migrate`

      if migrations.length > 0
        question =  "It looks like there are pending migrations in this changeset:\n"
        question << migrations + "\n"
        question << "Are you sure you want to deploy without migrations (y/n)?"
        answer = CLI.ui.ask(question)

        unless answer =~ /^y(es)?/i
          puts "Deploy aborted."
          exit(-1)
        end
      end
    end
  end

  before "deploy", "deploy:gate"
  before 'deploy', 'deploy:gate:schema'
  before "deploy:migrations", "deploy:gate"

  # ... rest of deploy.rb file

end