$ git clone -n https://src.fedoraproject.org/rpms/R-jquerylib.git /var/lib/mock/f42-build-side-1-3500778-45971/root/chroot_tmpdir/scmroot/R-jquerylib
Cloning into '/var/lib/mock/f42-build-side-1-3500778-45971/root/chroot_tmpdir/scmroot/R-jquerylib'...
$ git fetch origin 6dba96273719dcda437de38a2673b023935cdcb7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-jquerylib
 * [new ref]         6dba96273719dcda437de38a2673b023935cdcb7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6dba962 R-maint-sig mass rebuild