$ git clone -n https://src.fedoraproject.org/rpms/R-haven.git /var/lib/mock/f38-build-724213-99404/root/chroot_tmpdir/scmroot/R-haven
Cloning into '/var/lib/mock/f38-build-724213-99404/root/chroot_tmpdir/scmroot/R-haven'...
$ git fetch origin d81a17e2c9e257d1178c631345fda9e22678988a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-haven
 * [new ref]         d81a17e2c9e257d1178c631345fda9e22678988a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d81a17e R-maint-sig mass rebuild