testCases := []struct {
		name string

		// test inputs.
		revision string
		cfg      Config

		// expected results.
		wantRevision string
	}{
		{
			name:     "NoOverwriteEmptyInput",
			revision: "",
			cfg: Config{
				Prefix:   "default",
				Revision: "istio.io/rev=XXX",
			},
			wantRevision: "istio.io/rev=XXX",
		},
		{
			name:     "NoOverwriteNonEmptyInput",