End goal: add all commit authors to pull-request Cc:

Either do this at pull-request only, and add the Cc: to the mail template only, or add the Cc: labels to each tag and then grab the Cc's from tags and add them while sending the pull request.

Example: https://cgit.freedesktop.org/drm-misc/tag/?h=drm-misc-next-2018-03-21