Convert all authors to one author

[TidbitSoftware]

Hi,
Thanks for this great utility. We're looking to migrate a repository with a long history and a many contributing authors. Many of these authors are no longer in contact and we do not have an easy way of looking them up on GitHub, or contacting them and asking them to set up an account if one does not exist. In order to keep the new repository smallish, we were considering migrating from the last revision, and also making all existing files have the same author. Is this possible? Would we have to manually map all existing authors that we do not have info for to a single author in the authors file, or is there a way to set a default?

[TidbitSoftware]

As a follow up, are email addresses strictly required in the authors file?