$ git clone -n https://src.fedoraproject.org/rpms/plasma-desktop.git /var/lib/mock/f42-build-side-1-3585161-46903/root/chroot_tmpdir/scmroot/plasma-desktop
Cloning into '/var/lib/mock/f42-build-side-1-3585161-46903/root/chroot_tmpdir/scmroot/plasma-desktop'...
$ git fetch origin 19c131b20190f15c28d10406a454c0392adcbd08:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-desktop
 * [new ref]         19c131b20190f15c28d10406a454c0392adcbd08 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 19c131b 6.4.2