$ git clone -n https://src.fedoraproject.org/rpms/rust-unchecked-index.git /var/lib/mock/f40-build-2717862-72832/root/chroot_tmpdir/scmroot/rust-unchecked-index
Cloning into '/var/lib/mock/f40-build-2717862-72832/root/chroot_tmpdir/scmroot/rust-unchecked-index'...
$ git fetch origin dc450c9a2d84fe33a0a35f6bc1d601e645941ab0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-unchecked-index
 * [new ref]         dc450c9a2d84fe33a0a35f6bc1d601e645941ab0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dc450c9 Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild