$ git clone -n https://src.fedoraproject.org/rpms/jaxb-api.git /var/lib/mock/f40-build-2199464-51744/root/chroot_tmpdir/scmroot/jaxb-api
Cloning into '/var/lib/mock/f40-build-2199464-51744/root/chroot_tmpdir/scmroot/jaxb-api'...
$ git fetch origin d6e2c3db5db2c1a8ab6029f8cab52d3dbf65038e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jaxb-api
 * [new ref]         d6e2c3db5db2c1a8ab6029f8cab52d3dbf65038e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d6e2c3d Update to upstream version 4.0.1