$ git clone -n https://src.fedoraproject.org/rpms/R-rvest.git /var/lib/mock/f42-build-side-110318-58926488-6569309/root/chroot_tmpdir/scmroot/R-rvest
Cloning into '/var/lib/mock/f42-build-side-110318-58926488-6569309/root/chroot_tmpdir/scmroot/R-rvest'...
$ git fetch origin 7a1552b88463533974478f7252772c9f4596d826:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rvest
 * [new ref]         7a1552b88463533974478f7252772c9f4596d826 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7a1552b R-maint-sig mass rebuild