Allow running the `notowned` check when the local repository is dirty

[autarch]

Description

I'd like an option to run the notowned check for a dirty repo. Ideally, it would ignore files that are not staged when run this way.

Reasons

I'm setting this up for a work repo. We want to enforce the rule that all files have owners via the notowned check. We'd also like to use this as part of our pre-commit linting. However, this particular check always fails when run via a pre-commit hook because the repo is dirty.