Missing git information when uploading to coveralls

[michallaskowski]

Switching from Slather for technical reasons, there is not enough data in Coveralls, compared to our previous runs, so that new data is not displayed. We were tracking coverage on main branch, and in Pull Requests, but with xcov there is no possibility to specify branch's name or PR info.

Take a look at what Slather does: https://github.com/SlatherOrg/slather/blob/master/lib/slather/coverage_service/coveralls.rb#L313
xcov should allow to pass those parameters as arguments, or at least env variables in a similar manner.

Also, no idea why providing coveralls_repo_token makes it impossible to provide service_job_id and service_name 🤷‍♂️
This should also be possible, there is no reason not to provide it, as in docs https://docs.coveralls.io/api-reference
or as Slather does.

Happy to jump and implement the changes, given the maintainers agree.