TODO: Better CLI options

I'd rather have:

```
uv run scenarios.py --pip-version  "notatallshaw/pip@c4157d8dfb2823fc967549ccca08c150ab3df98b"
```

Than the current:

```
uv run scenarios.py --github-repo "notatallshaw/pip" --git-commit c4157d8dfb2823fc967549ccca08c150ab3df98b
```

The same for `compare.py `