$ git clone -n https://src.fedoraproject.org/rpms/R-DT.git /var/lib/mock/f40-build-1970539-25220/root/chroot_tmpdir/scmroot/R-DT
Cloning into '/var/lib/mock/f40-build-1970539-25220/root/chroot_tmpdir/scmroot/R-DT'...
$ git fetch origin 731be4ef89fdac51629b9428b31c4443fe535685:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-DT
 * [new ref]         731be4ef89fdac51629b9428b31c4443fe535685 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 731be4e R-maint-sig mass rebuild