$ git clone -n https://src.fedoraproject.org/rpms/R-data.table.git /var/lib/mock/f38-build-724165-99404/root/chroot_tmpdir/scmroot/R-data.table
Cloning into '/var/lib/mock/f38-build-724165-99404/root/chroot_tmpdir/scmroot/R-data.table'...
$ git fetch origin e2e06edb4b401251d7b253f671d612173525a2a9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-data.table
 * [new ref]         e2e06edb4b401251d7b253f671d612173525a2a9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e2e06ed Ignore vignettes