$ git clone -n https://src.fedoraproject.org/rpms/rust-jxl-frame.git /var/lib/mock/f40-build-2082590-49850/root/chroot_tmpdir/scmroot/rust-jxl-frame
Cloning into '/var/lib/mock/f40-build-2082590-49850/root/chroot_tmpdir/scmroot/rust-jxl-frame'...
$ git fetch origin 8fcffabb6f81ef389dbc7a7af829a903caec7b67:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-jxl-frame
 * [new ref]         8fcffabb6f81ef389dbc7a7af829a903caec7b67 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8fcffab Initial Fedora packaging (rhbz#2248924)