Fixed migration generator API usage
Fixed migration generator API usage

ActiveRecord provides an option to use timestamped
migration numbering. This is what the active_record
implementation looks like:

  if ActiveRecord::Base.timestamped_migrations
    Time.now.utc.strftime("%Y%m%d%H%M%S")
  else
    "%.3d" % (current_migration_number(dirname) + 1)
  end

I wonder if we want to support something like this
too?

With this commit, the following generator usage is
supported

  bundle exec rails generate migration Person

This will properly create a datamapper migration
file. However, running this migration via

  bundle exec rake db:migrate

still fails. This will change soon though.
datamapper/dm-rails,jhuckabee/rails3_datamapper