$ git clone -n https://src.fedoraproject.org/rpms/R-repurrrsive.git /var/lib/mock/f42-build-side-1-3501691-45976/root/chroot_tmpdir/scmroot/R-repurrrsive
Cloning into '/var/lib/mock/f42-build-side-1-3501691-45976/root/chroot_tmpdir/scmroot/R-repurrrsive'...
$ git fetch origin 6568b9d09bb6c025aa7e547f46b3c4e329aaed79:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-repurrrsive
 * [new ref]         6568b9d09bb6c025aa7e547f46b3c4e329aaed79 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6568b9d R-maint-sig mass rebuild