$ git clone -n https://src.fedoraproject.org/rpms/xz.git /var/lib/mock/f40-build-777672-129469/root/chroot_tmpdir/scmroot/xz
Cloning into '/var/lib/mock/f40-build-777672-129469/root/chroot_tmpdir/scmroot/xz'...
$ git fetch origin 0c09a6280b4a0c4fd7a9fc742c09469c95ff431f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xz
 * [new ref]         0c09a6280b4a0c4fd7a9fc742c09469c95ff431f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0c09a62 New version 5.4.6 (RHBZ#2260521)