Heroku::Rake::Task wrapper to work around exit status issue in `heroku run`

heroku.rake

module Heroku
  module Rake
    class Task
      attr_accessor :name
      def initialize(name)
        @name = name
      end

      def self.[](name)
        Heroku::Rake::Task.new(name)
      end

      def execute(options = {})
        cmd = "heroku run \"rake #{name}"
        cmd += "; echo \\$?\""
        cmd += "#{options[:app] ? " --app #{options[:app]}" : ""}"
        stdout = `#{cmd}`
        $stdout.puts stdout.lines.to_a[0...-1]
        exit_status = stdout.lines.to_a.last.chomp.to_i
        raise "Heroku task #{name} failed with exit status #{exit_status}" unless exit_status == 0
      end
    end
  end
end

namespace :heroku
  desc "Run example task on remote Heroku"
  task "example_task" do
    Heroku::Rake::Task["example_task"].execute({ :app => "example-app" })
  end
end

This is a quick hack to address heroku/legacy-cli#186, the symptom of which is heroku rake commands failing remotely but returning a successful exit status locally. Include the above Heroku module snippet in one of your lib/tasks/*.rake files, and then invoke a Heroku rake task from within any Rake task, a la:

Heroku::Rake::Task["some:task"].execute({ :app => "some-app" })