Using ActiveRecord Migrations outside of a Rails app

Rakefile

require "bundler/gem_tasks"
require "rspec/core/rake_task"

RSpec::Core::RakeTask.new(:spec)

task :default => :spec

require "erb"
require "yaml"
require "active_record"
include ActiveRecord::Tasks

root = File.expand_path("..", __FILE__)
DatabaseTasks.env = ENV["APP_ENV"] || "test"
DatabaseTasks.database_configuration = YAML.load(
  ERB.new(
    File.read(File.join(root, "config/database.yml"))
  ).result
)
DatabaseTasks.db_dir = File.join(root, "db")
DatabaseTasks.fixtures_path = File.join root, "test/fixtures"
DatabaseTasks.migrations_paths = [File.join(root, "db/migrate")]
DatabaseTasks.root = root
ActiveRecord::Base.schema_format = :sql

task :environment do
  ActiveRecord::Base.configurations = DatabaseTasks.database_configuration
  ActiveRecord::Base.establish_connection(DatabaseTasks.env.to_sym)
end

load 'active_record/railties/databases.rake'