Implement self-update recovery (T-403)

app-modern/cmd/softboxupdater/main_test.go

@@ -0,0 +1,14 @@
+package main
+
+import "testing"
+
+func TestRunRejectsIncompleteAndDuplicateArguments(t *testing.T) {
+	if err := run(nil); err == nil {
+		t.Fatal("run(nil) succeeded")
+	}
+	if err := run([]string{
+		"--pid", "1", "--pid", "2", "--staging", "/root/staging/update-1234", "--target", "/root/app",
+	}); err == nil {
+		t.Fatal("run() accepted duplicate --pid")
+	}
+}