cmd/containerboot: add tests.

Signed-off-by: David Anderson <danderson@tailscale.com>

cmd/containerboot/test_tailscaled.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+#
+# This is a fake tailscale CLI that records its arguments, symlinks a
+# fake LocalAPI socket into place, and does nothing until terminated.
+#
+# It is used by main_test.go to test the behavior of containerboot.
+
+set -eu
+
+echo $0 $@ >>$TS_TEST_RECORD_ARGS
+
+socket=""
+while [[ $# -gt 0 ]]; do
+	case $1 in
+		--socket=*)
+			socket="${1#--socket=}"
+			shift
+			;;
+		--socket)
+			shift
+			socket="$1"
+			shift
+			;;
+		*)
+			shift
+			;;
+	esac
+done
+
+if [[ -z "$socket" ]]; then
+	echo "didn't find socket path in args"
+	exit 1
+fi
+
+ln -s "$TS_TEST_SOCKET" "$socket"
+
+while true; do sleep 1; done