berks:tldr:9b755

The command berks contingent ${cookbook} is not a valid command in the context of Berkshelf. Typically, in Berkshelf, the command would be berks upload ${cookbook} to upload a cookbook to a Chef server or berks install to fetch and install the dependencies specified in the Berksfile.

However, if we assume the command is: berks contingent ${cookbook}, it is likely a custom command added by someone to the Berkshelf project. Without further information, it is difficult to determine its exact functionality. It may be a command to check the dependencies or related cookbooks that are contingent on a particular cookbook (${cookbook} could be a placeholder for a specific cookbook name). However, without more context or information on the specific implementation, it is challenging to provide a more specific explanation.