I'm not a security expert, but if you're reading this and wondering what to do, a good start could be to just assume your repo was accessed, and so to run a tool like gitleaks against your repo. If it detects anything sensitive, I'd see about revoking/deleting those secrets right away.

In general, it's good practice not to check anything sensitive into source code for precisely this reason (if your code is compromised you don't want your secrets to be as well). So it'd also be good practice to add something like gitleaks into your CI/CD pipeline for the future.