$ git clone -n https://src.fedoraproject.org/rpms/R-gert.git /var/lib/mock/f38-build-724506-99434/root/chroot_tmpdir/scmroot/R-gert
Cloning into '/var/lib/mock/f38-build-724506-99434/root/chroot_tmpdir/scmroot/R-gert'...
$ git fetch origin 2224803e2d1a9100a2bf1e0e584d280f34f74836:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gert
 * [new ref]         2224803e2d1a9100a2bf1e0e584d280f34f74836 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2224803 Ignore vignettes