fastlane1.rb

  before_all do |options, params|
    build_number =
      # highest priority has build_number passes as parameter to the fastlane
      params[:build_number] || 
      # we use Circle CI - build number is autoincremented on CI
      # we can get it from environment
      ENV["CIRCLE_BUILD_NUM"] ||
      # if you run fastlane localy on your machine it gets build number
      # from Circle CI by using their API
      get_last_circleci_build_number
  end