$ git clone -n https://src.fedoraproject.org/rpms/R-cellranger.git /var/lib/mock/f40-build-1930437-25111/root/chroot_tmpdir/scmroot/R-cellranger
Cloning into '/var/lib/mock/f40-build-1930437-25111/root/chroot_tmpdir/scmroot/R-cellranger'...
$ git fetch origin 1d536213db8b4b638751e51926e42b71549bc5f0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-cellranger
 * [new ref]         1d536213db8b4b638751e51926e42b71549bc5f0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1d53621 R-maint-sig mass rebuild