$ git clone -n https://src.fedoraproject.org/rpms/R-utf8.git /var/lib/mock/f42-build-side-110318-58926882-6569309/root/chroot_tmpdir/scmroot/R-utf8
Cloning into '/var/lib/mock/f42-build-side-110318-58926882-6569309/root/chroot_tmpdir/scmroot/R-utf8'...
$ git fetch origin 3cf1d9d19bdb6ebe7bf6bcd8a091fbc7a795fc01:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-utf8
 * [new ref]         3cf1d9d19bdb6ebe7bf6bcd8a091fbc7a795fc01 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3cf1d9d R-maint-sig mass rebuild