$ git clone -n https://src.fedoraproject.org/rpms/libxml2.git /var/lib/mock/f42-build-side-1-3501329-45974/root/chroot_tmpdir/scmroot/libxml2
Cloning into '/var/lib/mock/f42-build-side-1-3501329-45974/root/chroot_tmpdir/scmroot/libxml2'...
$ git fetch origin 6d3dc968d88e0520bca45d195560582de2515205:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libxml2
 * [new ref]         6d3dc968d88e0520bca45d195560582de2515205 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6d3dc96 Update to 2.12.10