This makes this codeowner mechanism behave differently than the native
one, but there's no other way to avoid rerequesting reviews from teams
when a member already reviewed the PR.
The automation should never rerequest reviews from users that already
reviewed the changes, which is what was happening before this change:
https://github.com/NixOS/nixpkgs/pull/347354#event-14570645380
Also reorder the arguments to make more sense
Also post a comment in case base branch is wrong
This guides newcomers in how to smoothly handle the potentially scary
situation of having thousands of commits listed in a PR.
While CI shows the same, people might not even look at CI if the PR
looks botched.
