$ git clone -n https://src.fedoraproject.org/rpms/plasma-oxygen.git /var/lib/mock/f42-build-side-1-3578407-46814/root/chroot_tmpdir/scmroot/plasma-oxygen
Cloning into '/var/lib/mock/f42-build-side-1-3578407-46814/root/chroot_tmpdir/scmroot/plasma-oxygen'...
$ git fetch origin 1254c52fefe55a06306608b7dc4b878ac46e1bbb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-oxygen
 * [new ref]         1254c52fefe55a06306608b7dc4b878ac46e1bbb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1254c52 6.4.1