$ git clone -n https://src.fedoraproject.org/rpms/gn.git /var/lib/mock/f40-build-2442791-61065/root/chroot_tmpdir/scmroot/gn
Cloning into '/var/lib/mock/f40-build-2442791-61065/root/chroot_tmpdir/scmroot/gn'...
$ git fetch origin 3de364052b0df84e9b28b13d1f3e9aca52e1979c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gn
 * [new ref]         3de364052b0df84e9b28b13d1f3e9aca52e1979c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3de3640 Update to version 2146