ActiveRecord migration - when reversible.up/reversible.down feature was introduced?

Question

I'm currently in the process of upgrading old legacy Rails app and trying to find the exact version number when this reversible.up, reversible.down block feature was introduced.

class SplitNameMigration < ActiveRecord::Migration
  def change
    add_column :users, :first_name, :string
    add_column :users, :last_name, :string

    reversible do |dir|
      User.reset_column_information
      User.all.each do |u|
        dir.up   { u.first_name, u.last_name = u.full_name.split(' ') }
        dir.down { u.full_name = "#{u.first_name} #{u.last_name}" }
        u.save
      end
    end
  end
end

Does anyone know?