$ git clone -n https://src.fedoraproject.org/rpms/R-RM2.git /var/lib/mock/f42-build-side-110318-58926348-6569309/root/chroot_tmpdir/scmroot/R-RM2
Cloning into '/var/lib/mock/f42-build-side-110318-58926348-6569309/root/chroot_tmpdir/scmroot/R-RM2'...
$ git fetch origin fc9e0c77e92562686427439466ac84c418e12675:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-RM2
 * [new ref]         fc9e0c77e92562686427439466ac84c418e12675 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fc9e0c7 R-maint-sig mass rebuild