ActiveRecord Sqlite auto connection + migration without Rails in one file (AR 4)

db.rb

require 'active_record'
require 'fileutils'

ActiveRecord::Base.logger = Logger.new(STDERR)

db = "db/#{ENV['RACK_ENV']}.sqlite3"
if not File.exists? db
  `sqlite3 #{db} '' `
end

ActiveRecord::Base.establish_connection(
  :adapter => "sqlite3",
  :database => db
)

class FeedMigration < ActiveRecord::Migration
  def change
    create_table :feeds do |t|
      t.string :url
      t.string :title
      t.datetime :lastmodified
      t.string :etag
      t.timestamps
    end
  end
end


migrations = [FeedMigration]

migrations = migrations.each_with_index.map do |m,i|
  proxy = ActiveRecord::MigrationProxy.new(m.to_s, i.to_s, '', '')
  proxy.define_singleton_method(:load_migration, -> { m })
  proxy
end

ActiveRecord::Migrator.new(:up, migrations, nil).migrate


class Feed < ActiveRecord::Base
end