rails-i18n-updater

https://github.com/zargony/rails-i18n-updater

This Rails plugin provides the rake task i18n:update to download the latest core translations to vendor/rails-locales. On application start, the plugin automatically prepends downloaded core translations to the I18n load_path. So the downloaded core translations are automatically used in your application, but you can still override the defaults in your own locale files.