If a group is used in project.config that does not have a valid UUID in the groups file (either its not present at all, or the UUID is "?") try to resolve the group by name and fix the groups file automatically.
If a change was pushed directly to the branch, apply a new commit that resolves the group, and warn the user that the group was resolved.
If a change was pushed for review, amend the commit with the group resolution and warn the user that patch set 1 is not the same commit they pushed (due to the group resolution).