Investigate storing co-authors in the (global) git config. E.g.

[git-mob-coauthors]
  rk = Richard Kotze <rk@findmypast.com>
  ea = Elliot Alderson <mr.robot@fsociety.com>

It's a simpler way to manage a list of authors because we can drop extra dependencies such as a separate file and a JSON parser. Users who store their .gitconfig in their dotfiles will have their co-authors become portable for free.

Do a benchmark, is there a noticeable difference in execution time?

Low priority, our current JSON solution has been working fine. But perhaps worth checking out before v1.

Follow-up would be to add co-authors via git-mob so users never have to switch context and edit a separate file.