$ git clone -n https://src.fedoraproject.org/rpms/R-gert.git /var/lib/mock/f40-build-1944429-25177/root/chroot_tmpdir/scmroot/R-gert
Cloning into '/var/lib/mock/f40-build-1944429-25177/root/chroot_tmpdir/scmroot/R-gert'...
$ git fetch origin baab48b7a3385b9639a086f827d83b87c8c03850:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gert
 * [new ref]         baab48b7a3385b9639a086f827d83b87c8c03850 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at baab48b R-maint-sig mass rebuild