$ git clone -n https://src.fedoraproject.org/rpms/R-errors.git /var/lib/mock/f40-build-1930423-25111/root/chroot_tmpdir/scmroot/R-errors
Cloning into '/var/lib/mock/f40-build-1930423-25111/root/chroot_tmpdir/scmroot/R-errors'...
$ git fetch origin 9ee09c100214ad7170e7033b3c82033418450d43:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-errors
 * [new ref]         9ee09c100214ad7170e7033b3c82033418450d43 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9ee09c1 R-maint-sig mass rebuild