$ git clone -n https://src.fedoraproject.org/rpms/rust-rustc_version.git /var/lib/mock/f40-build-2653650-66902/root/chroot_tmpdir/scmroot/rust-rustc_version
Cloning into '/var/lib/mock/f40-build-2653650-66902/root/chroot_tmpdir/scmroot/rust-rustc_version'...
$ git fetch origin b83f13d244f0a271dcfe3ba13a7bd5a72c4505c3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-rustc_version
 * [new ref]         b83f13d244f0a271dcfe3ba13a7bd5a72c4505c3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b83f13d Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild