$ git clone -n https://src.fedoraproject.org/rpms/R-keyring.git /var/lib/mock/f38-build-724753-99479/root/chroot_tmpdir/scmroot/R-keyring
Cloning into '/var/lib/mock/f38-build-724753-99479/root/chroot_tmpdir/scmroot/R-keyring'...
$ git fetch origin df508f066f674c158c61ea83b0c30a80e68f48ce:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-keyring
 * [new ref]         df508f066f674c158c61ea83b0c30a80e68f48ce -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at df508f0 R-maint-sig mass rebuild