Do you mean code that is only used by you in dev?

yea correct

I don't know of a good convention, but in my experience, such code can be valuable to other developers on the team. For example if you have your own code that queries the database or fiddle with other parts of the system! If you keep these commits isolated, which I believe you already do, I would try to explain what's in each commit.

I normally use 2 guidelines for stuff like these: 1. keep them in separate commits (per Kent Beck's Tidy First(?)) 2. prefix the message with a dev: type per https://www.conventionalcommits.org/