Add filtering script

filter.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-3.0-or-later
+set -euo pipefail
+export FILTER_BRANCH_SQUELCH_WARNING=1
+git branch -D filtered
+git switch -c filtered
+git filter-branch -f --tree-filter "rm -f $(rg --files-without-match 'SPDX-License-Identifier: (L)?GPL-3.0-or-later' -g '/u??/**/*' | tr '\n' ' ')" HEAD
+git push -f -u filtered filtered
+git switch -