Implemented ActiveRecord::Migrations#copy based on James Adam's idea

ActiveRecord::Migration#copy allows to copy migrations from one place
to another, changing migrations versions and adding scope to filename.

For example:
ActiveRecord::Migration.copy("db/migrate",
        :blog_engine => "vendor/gems/blog/db/migrate")

will copy all migrations from vendor/gems/blog/db/migrate to db/migrate
with such format:

Versions of copied migrations will be reversioned to be appended after
migrations that already exists in db/migrate

1 files changed, 6 insertions, 0 deletions

diff --git a/activerecord/lib/rails/generators/active_record.rb b/activerecord/lib/rails/generators/active_record.rb
index 26bc977e19..4b3d1db216 100644
--- a/activerecord/lib/rails/generators/active_record.rb
+++ b/activerecord/lib/rails/generators/active_record.rb
@@ -14,6 +14,12 @@ module ActiveRecord
       def self.base_root
         File.dirname(__FILE__)
       end
+
+      # Implement the required interface for Rails::Generators::Migration.
+      def self.next_migration_number(dirname) #:nodoc:
+        next_migration_number = current_migration_number(dirname) + 1
+        ActiveRecord::Migration.next_migration_number(next_migration_number)
+      end
     end
   end
 end