scripts/check_license_headers.sh: delete, rewrite as a Go test

Updates tailscale/corp#29650

Change-Id: Iad4e4ccd9d68ebb1d1a12f335cc5295d0bd05b60
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

scripts/check_license_headers.sh

@@ -1,77 +0,0 @@
-#!/bin/sh
-#
-# Copyright (c) Tailscale Inc & AUTHORS
-# SPDX-License-Identifier: BSD-3-Clause
-#
-# check_license_headers.sh checks that all Go files in the given
-# directory tree have a correct-looking Tailscale license header.
-
-check_file() {
-    got=$1
-
-    want=$(cat <<EOF
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-EOF
-    )
-    if [ "$got" = "$want" ]; then
-        return 0
-    fi
-    return 1
-}
-
-if [ $# != 1 ]; then
-    echo "Usage: $0 rootdir" >&2
-    exit 1
-fi
-
-fail=0
-for file in $(find $1 \( -name '*.go' -or -name '*.tsx' -or -name '*.ts' -not -name '*.config.ts' \) -not -path '*/.git/*' -not -path '*/node_modules/*'); do
-    case $file in
-        $1/tempfork/*)
-            # Skip, tempfork of third-party code
-        ;;
-        $1/wgengine/router/ifconfig_windows.go)
-            # WireGuard copyright.
-        ;;
-        $1/cmd/tailscale/cli/authenticode_windows.go)
-            # WireGuard copyright.
-        ;;
-        *_string.go)
-          # Generated file from go:generate stringer
-        ;;
-        $1/control/controlbase/noiseexplorer_test.go)
-          # Noiseexplorer.com copyright.
-        ;;
-        */zsyscall_windows.go)
-            # Generated syscall wrappers
-        ;;
-        $1/util/winutil/subprocess_windows_test.go)
-            # Subprocess test harness code
-        ;;
-        $1/util/winutil/testdata/testrestartableprocesses/main.go)
-            # Subprocess test harness code
-        ;;
-        *$1/k8s-operator/apis/v1alpha1/zz_generated.deepcopy.go)
-            # Generated kube deepcopy funcs file starts with a Go build tag + an empty line
-            header="$(head -5 $file | tail -n+3 )"
-        ;;
-        $1/derp/xdp/bpf_bpfe*.go)
-            # Generated eBPF management code
-        ;;
-        *)
-           header="$(head -2 $file)"
-        ;;
-    esac
-    if [ ! -z "$header" ]; then
-            if ! check_file "$header"; then
-                fail=1
-                echo "${file#$1/} doesn't have the right copyright header:"
-                echo "$header" | sed -e 's/^/    /g'
-            fi
-    fi
-done
-
-if [ $fail -ne 0 ]; then
-    exit 1
-fi