Rails migrations which automatically put the new filename in your paste buffer

migration.rb

# this monkey-patches code defined in railties-3.1.0.rc1/lib/rails/generators/migration.rb
# (obviously, this might differ very slightly in the latest release candidate)

module Rails
  module Generators
    module Migration
      module ClassMethods
      # differs from the "real" version by only one line
      def migration_template(source, destination=nil, config={})
        destination = File.expand_path(destination || source, self.destination_root)

        migration_dir = File.dirname(destination)
        @migration_number     = self.class.next_migration_number(migration_dir)
        @migration_file_name  = File.basename(destination).sub(/\.rb$/, '')
        @migration_class_name = @migration_file_name.camelize

        destination = self.class.migration_exists?(migration_dir, @migration_file_name)

        if !(destination && options[:skip]) && behavior == :invoke
          if destination && options.force?
            remove_file(destination)
          elsif destination
            raise Error, "Another migration is already named #{@migration_file_name}: #{destination}"
          end
          destination = File.join(migration_dir, "#{@migration_number}_#{@migration_file_name}.rb")

          system("printf #{destination} | pbcopy") # this is that one line
        end

        template(source, destination, config)
      end
    end
  end
end

# note that if you change the line above, reversing the order of migration_number and
# migration_file_name, you can also get migration filenames which are not, from the perspective
# of experienced Unix users, completely fucking insane in their incomprehensible disregard
# for the incredible usefulness of tab completion (a baffling flaw also shared by Rails's
# config.ru default rackup file name).

# HOWEVER, making that change very likely breaks rake db:migrate, so I'm not going to advocate that
# unless I find time to make sure it works. :-)

Oops. Yeah, I just figured since the other places needed it, it'd be needed there. In fact it's not, so nice catch.