$ git clone -n https://src.fedoraproject.org/rpms/R-disposables.git /var/lib/mock/f43-build-58894998-6569073/root/chroot_tmpdir/scmroot/R-disposables
Cloning into '/var/lib/mock/f43-build-58894998-6569073/root/chroot_tmpdir/scmroot/R-disposables'...
$ git fetch origin 5ffd58249506212ca48e75f30387fb035b800dd1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-disposables
 * [new ref]         5ffd58249506212ca48e75f30387fb035b800dd1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5ffd582 R-maint-sig mass rebuild