Add kustomization source and decryption provider flags

internal/flags/decryption_provider.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2020 The Flux CD contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flags
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/fluxcd/toolkit/internal/utils"
+)
+
+var supportedDecryptionProviders = []string{"sops"}
+
+type DecryptionProvider string
+
+func (d *DecryptionProvider) String() string {
+	return string(*d)
+}
+
+func (d *DecryptionProvider) Set(str string) error {
+	if !utils.ContainsItemString(supportedDecryptionProviders, str) {
+		return fmt.Errorf("unsupported decryption provider '%s', must be one of: %s",
+			str, strings.Join(supportedDecryptionProviders, ", "))
+
+	}
+	*d = DecryptionProvider(str)
+	return nil
+}
+
+func (d *DecryptionProvider) Type() string {
+	return "decryptionProvider"
+}
+
+func (d *DecryptionProvider) Description() string {
+	return fmt.Sprintf("decryption provider, available options are: (%s)", strings.Join(supportedDecryptionProviders, ", "))
+}