Hooks for tddium to deploy to heroku that I personally find very useful - with plenty of scope for improvement no doubt!

tddium.rake

# RAILS_ROOT/lib/task/tddium.rake
#
# http://blog.tddium.com/2012/05/09/heroku-continuous-deployment/
# https://gist.github.com/semipermeable/2639790
# https://github.com/javierjulio
namespace :tddium do
  desc "Tddium pre-worker hook that sets up test db"
  task :worker_setup_hook do
    Bundler.with_clean_env do
        system "rake db:test:prepare"
    end
  end
  
  desc "Tddium post build hook that deploys to Heroku staging if tests pass"
  task :post_build_hook do
    # This build hook should only run after CI builds.
    #
    # There are other cases where we'd want to run something after every build,
    # or only after manual builds.
    abort "Not started from CI" unless ENV["TDDIUM_MODE"] == "ci"
    abort "Build failed" unless ENV["TDDIUM_BUILD_STATUS"] == "passed"

    heroku_email = ENV["HEROKU_EMAIL"]
    heroku_api_key = ENV["HEROKU_API_KEY"]
    current_branch = `git symbolic-ref HEAD 2>/dev/null | cut -d"/" -f 3-`.strip
    app_name = ENV["HEROKU_APP_NAME"]
    push_target = "git@heroku.com:#{app_name}.git"

    # We could improve this script by checking which branch we are on and using
    # different heroku apps to push to
    puts "Current branch: #{current_branch}"
    abort "invalid current branch" unless current_branch

    File.open(File.expand_path("~/.netrc"), "a+") do |f|
      ['api', 'code'].each do |host|
        f.puts "machine #{host}.heroku.com"
        f.puts "  login #{heroku_email}"
        f.puts "  password #{heroku_api_key}"
      end
    end

    puts "Pushing to heroku: #{push_target}"
    system "git push #{push_target} HEAD:master" or abort "could not push to #{push_target}"

    # http://stackoverflow.com/questions/14452734/heroku-toolbelt-not-working-with-rake-tasks
    # Related issue in db.rake also using Bundler.with_clean_env
    Bundler.with_clean_env do
      # http://blog.carbonfive.com/2013/08/12/minimizing-downtime-when-deploying-to-heroku/
      # This provided the inspiration for these amendments, though we've stopped short of
      # precompiling the slug and assets
      puts "Checking to see if there are new migrations"
      system "git remote add heroku #{push_target}"
      system "git fetch heroku"
      s = `git diff HEAD heroku/master --name-only -- db | wc -l | tr -d ' \n'`.to_i

      if s > 0
        puts "Enabling Maintenance mode..."
        system "heroku maintenance:on --app #{app_name}" or abort "could not enable for app #{app_name}"

        puts "Running Heroku Migrations..."
        system "heroku run rake db:migrate --app #{app_name}" or abort "aborted migrations for app #{app_name}"

        puts "Disabling Maintenance mode..."
        system "heroku maintenance:off --app #{app_name}" or abort "could not disable for app #{app_name}"

        puts "Restarting Heroku..."
        system "heroku ps:restart --app #{app_name}" or abort "aborted heroku restart for app #{app_name}"
      end
    end
  end
end