$ git clone -n https://src.fedoraproject.org/rpms/rust.git /var/lib/mock/f42-build-3272106-41276/root/chroot_tmpdir/scmroot/rust
Cloning into '/var/lib/mock/f42-build-3272106-41276/root/chroot_tmpdir/scmroot/rust'...
$ git fetch origin ad5a8095c85ce34e4faac6fb39d184c443e9b0c8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust
 * [new ref]         ad5a8095c85ce34e4faac6fb39d184c443e9b0c8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ad5a809 Update to Rust 1.85.0