For chellcheck, see [0] and documentation around there.

Here, "new" means the checker should tolerate old violations, but should refuse new ones.
If pairing the violations is hard, the checker should at least prevent the number of violations from increasing.

Some violations contradict the current guidelines, so some work needs to be done to unify them.

Optionally, add a non-voting checker to list all current violations, so they can be located more easily.

[0] https://github.com/koalaman/shellcheck#user-content-installing