$ git clone -n https://src.fedoraproject.org/rpms/rust-jxl-render.git /var/lib/mock/f42-build-3273563-41312/root/chroot_tmpdir/scmroot/rust-jxl-render
Cloning into '/var/lib/mock/f42-build-3273563-41312/root/chroot_tmpdir/scmroot/rust-jxl-render'...
$ git fetch origin 954589caafac01f6af4ffb7fda2e78932868c1db:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-jxl-render
 * [new ref]         954589caafac01f6af4ffb7fda2e78932868c1db -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 954589c no longer needed