$ git clone -n https://src.fedoraproject.org/rpms/varnish.git /var/lib/mock/f42-build-3490737-45854/root/chroot_tmpdir/scmroot/varnish
Cloning into '/var/lib/mock/f42-build-3490737-45854/root/chroot_tmpdir/scmroot/varnish'...
$ git fetch origin 66c48ec0410ba6724967835405ebd3369153ab2c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/varnish
 * [new ref]         66c48ec0410ba6724967835405ebd3369153ab2c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 66c48ec Fix for eln build (merged from yselkowitz)