$ git clone -n https://src.fedoraproject.org/rpms/rust-jxl-frame.git /var/lib/mock/f42-build-3402187-45132/root/chroot_tmpdir/scmroot/rust-jxl-frame
Cloning into '/var/lib/mock/f42-build-3402187-45132/root/chroot_tmpdir/scmroot/rust-jxl-frame'...
$ git fetch origin 430b9d92b85a66085b7b4621ecb62434ca2e92a7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-jxl-frame
 * [new ref]         430b9d92b85a66085b7b4621ecb62434ca2e92a7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 430b9d9 no longer needed