I can't use `centpkg mockbuild` in most cases.
Reason unkown

Severity: no known way to mockbuild from custom branch name from a fork

Expectation:
For every configuration, there should be at least 1 working way, ideally the same for all cases.
(that is `centpkg --release=c9s mockbuild` should successfuly build a package no matter what branch name, repo or fork I am in)

I demonstrate it on a trivial RHEL 9 / C9S package `mariadb-connector-odbc.
But the choice of the package doesn't matter as far as I can tell.

I tried:
1) running `centpkg mockbuild` on a `c9s` branch
2) running `centpkg --release=c9s mockbuild` on a `c9s` branch
3) running `centpkg mockbuild` on a (custom) `test_build` branch
4) running `centpkg --release=c9s mockbuild` on a (custom) `test_build` branch
5) running `centpkg mockbuild` on a (custom) `test_build0` branch

Results:
1) pass
2) unexplained fail
3) explained fail
4) unexplained fail, likely same as (2)
5) very weird fail, different than (3)

I've uploaded all data here: http://download.eng.brq.redhat.com/archive/mschorm/centpkg_mockbuild/

The:
1) is in "without-release-c9s"
2) is in "with-release-c9s"
3), (4) and (5) is in "branched"
directories