CI: use git-core to reduce number of dependencies
CI: use git-core to reduce number of dependencies

We don't need full git here

Signed-off-by: Martin Basti <388356a3851efe39ff0604de6d8fb2e16e10a0b7@redhat.com>

fr34k8/atomic-reactor,projectatomic/atomic-reactor,projectatomic/atomic-reactor,fr34k8/atomic-reactor