hook_og_role_grant() and hook_og_role_revoke() don't have a clear picture of role changes

The hooks hook_og_role_grant() and hook_og_role_revoke() have a problem: they are each invoked for each role change for a membership. This means that reacting to changed in specific roles quickly gets messy.

Suppose I want to do something such as send an email when a user is granted the 'member' role, but NOT when they are also an editor.

function mymodule_og_role_grant($entity_type, $gid, $uid, $rid) {
  if ($rid == MEMBER RID) {
    if ({user isn't also an editor}) {
      // Do something
    }
  }
}

That seems to me to have potential problems. What if the user is being granted BOTH the member and editor roles at the same time? Which order they are being granted in? If editor is granted first, then you should be okay. If member is granted first, then this function doesn't stand a chance.

I think there needs to be a hook that's invoked only once when roles are changed for a user, so that implementations can compare before and after cleanly.

However, that's going to be a easier said than done, as the whole of the API around role changes works with single changes: og_role_grant() / og_role_revoke().