$ git clone -n https://src.fedoraproject.org/rpms/plasma-activities.git /var/lib/mock/f42-build-side-1-3533138-46342/root/chroot_tmpdir/scmroot/plasma-activities
Cloning into '/var/lib/mock/f42-build-side-1-3533138-46342/root/chroot_tmpdir/scmroot/plasma-activities'...
$ git fetch origin c38783b8719abe683e80f712fb5f7b6cd85f4f03:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-activities
 * [new ref]         c38783b8719abe683e80f712fb5f7b6cd85f4f03 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c38783b 6.3.5