$ git clone -n https://src.fedoraproject.org/rpms/plasma-activities.git /var/lib/mock/f42-build-side-1-3569515-46747/root/chroot_tmpdir/scmroot/plasma-activities
Cloning into '/var/lib/mock/f42-build-side-1-3569515-46747/root/chroot_tmpdir/scmroot/plasma-activities'...
$ git fetch origin 06756c96e803ad290988eea7a8d485b8c535988a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-activities
 * [new ref]         06756c96e803ad290988eea7a8d485b8c535988a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 06756c9 6.4.0