11 files changed is better than 92. :)

I didn't see anything to change in the documentation; we still end up with a temp folder called sample_repo, which pytest renames to sample_repo0.

If you end up merging this, I think you should add a couple tests for commands you'd like to see covered, and ask any questions you have about working with the test suite. I don't have any ambitions to add a bunch of tests; my goal was to help get a test suite off the ground. If you want help with testing I'm happy to do more, but I think the bigger priority is that you're comfortable working with what's started here.

I would note that while using git-dummy is perfectly reasonable and understandable, I don't think it's as fast as copying a static repo. I think it might be reasonable to have a git-dummy call per test module, but I don't think you'd want a separate call per test function. I think the git-dummy call took about 2 seconds on my system, but I didn't benchmark that at all. I just noticed it went from ~6.3s for the test run with the static repo to ~8.3s using git-dummy. That would add up fast. You can start to see the impact by changing the scope of the tmp_repo() fixture from session to function. That runs the fixture once per test function rather than once for the whole session. For me, that's 8.3s -> 10.0s.

It's all good, you'll figure out how much test coverage is helpful to have without slowing down your development process. :)