$ git clone -n https://src.fedoraproject.org/rpms/jaxb.git /var/lib/mock/f40-build-2125576-50779/root/chroot_tmpdir/scmroot/jaxb
Cloning into '/var/lib/mock/f40-build-2125576-50779/root/chroot_tmpdir/scmroot/jaxb'...
$ git fetch origin e8cfeeec9bcceb1e899a73c3ab409d1d5416330f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jaxb
 * [new ref]         e8cfeeec9bcceb1e899a73c3ab409d1d5416330f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e8cfeee Update to upstream version 4.0.4