$ git clone -n https://src.fedoraproject.org/rpms/R-later.git /var/lib/mock/f38-build-724194-99404/root/chroot_tmpdir/scmroot/R-later
Cloning into '/var/lib/mock/f38-build-724194-99404/root/chroot_tmpdir/scmroot/R-later'...
$ git fetch origin 40e7c4ae6cd0608c8947c9e8f16da7b4f53bc6a3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-later
 * [new ref]         40e7c4ae6cd0608c8947c9e8f16da7b4f53bc6a3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 40e7c4a Ignore vignettes