$ git clone -n https://src.fedoraproject.org/rpms/xfdesktop.git /var/lib/mock/f41-build-side-1-2671345-29139/root/chroot_tmpdir/scmroot/xfdesktop
Cloning into '/var/lib/mock/f41-build-side-1-2671345-29139/root/chroot_tmpdir/scmroot/xfdesktop'...
$ git fetch origin 18e67d5955f2952f8db41b0c4f75faa8e2941233:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xfdesktop
 * [new ref]         18e67d5955f2952f8db41b0c4f75faa8e2941233 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 18e67d5 Fix setting default background