$ git clone -n https://src.fedoraproject.org/rpms/libb2.git /var/lib/mock/f45-build-15882-480/root/chroot_tmpdir/scmroot/libb2
Cloning into '/var/lib/mock/f45-build-15882-480/root/chroot_tmpdir/scmroot/libb2'...
$ git fetch origin d37de09baa2293d1f905293ad37e29f269dfdeb2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libb2
 * [new ref]         d37de09baa2293d1f905293ad37e29f269dfdeb2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d37de09 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild