$ git clone -n https://src.fedoraproject.org/rpms/shim-unsigned-x64.git /var/lib/mock/f38-build-side-42-init-devel-709135-27226/root/chroot_tmpdir/scmroot/shim-unsigned-x64
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-709135-27226/root/chroot_tmpdir/scmroot/shim-unsigned-x64'...
$ git fetch origin 5d3ab28756291a725d309da8f595de4a6ac8da7a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/shim-unsigned-x64
 * [new ref]         5d3ab28756291a725d309da8f595de4a6ac8da7a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5d3ab28 Update to shim-15.6