List installed gems with newer versions available
$ bundle outdated [GEM] [--local] [--pre] [--source] [--strict]
--local: Do not attempt to fetch gems remotely and use the gem cache instead
--pre: Check for newer pre-release gems
--source: Check against a specific source
--strict: Display outdated gems that match the dependency requirements.
Outdated lists the names and versions of gems that have a newer version available in the given source. Calling outdated with [GEM [GEM]] will only check for newer versions of the given gems. By default, available prerelease gems will be ignored.