See, that requires some argument of who it's for. Legally, copyright is established the moment something is created. (Hope you have proof.) I don't think you'd be able to claim _damages_ by sneaking your copyrighted code into the company repository, but other than that, I really have no idea how this would play out in court. It seems very risky but it's not obvious. I'd be interested in reading about cases in this middle area, if there have been any.

But anyway, I focused mostly on ethics. The specific situation you describe is ethically dubious, I agree, but I'm interested in where the line is and it's just not as clear as some are suggesting.

Copyright law is its own can of worms and is not the same as what's ethical. But, it does govern risk and practicality.