$ git clone -n https://src.fedoraproject.org/rpms/R-dplyr.git /var/lib/mock/f42-build-side-110318-58924800-6569303/root/chroot_tmpdir/scmroot/R-dplyr
Cloning into '/var/lib/mock/f42-build-side-110318-58924800-6569303/root/chroot_tmpdir/scmroot/R-dplyr'...
$ git fetch origin cd57188a7645cf18daedae34481fa9c16df292d3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-dplyr
 * [new ref]         cd57188a7645cf18daedae34481fa9c16df292d3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cd57188 R-maint-sig mass rebuild