$ git clone -n https://src.fedoraproject.org/rpms/R-sys /var/lib/mock/f39-build-1588618-38226/root/chroot_tmpdir/scmroot/R-sys
Cloning into '/var/lib/mock/f39-build-1588618-38226/root/chroot_tmpdir/scmroot/R-sys'...
$ git fetch origin 7fdff74bc7fd7323fedc6cc7eee56058f9ae4e34:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-sys
 * [new ref]         7fdff74bc7fd7323fedc6cc7eee56058f9ae4e34 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7fdff74 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild