lib/config: Change folder type attribute to a FolderType type

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3032

lib/config/foldertype.go

@@ -0,0 +1,41 @@
+// Copyright (C) 2016 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package config
+
+type FolderType int
+
+const (
+	FolderTypeReadWrite FolderType = iota // default is readwrite
+	FolderTypeReadOnly
+)
+
+func (t FolderType) String() string {
+	switch t {
+	case FolderTypeReadWrite:
+		return "readwrite"
+	case FolderTypeReadOnly:
+		return "readonly"
+	default:
+		return "unknown"
+	}
+}
+
+func (t FolderType) MarshalText() ([]byte, error) {
+	return []byte(t.String()), nil
+}
+
+func (t *FolderType) UnmarshalText(bs []byte) error {
+	switch string(bs) {
+	case "readwrite":
+		*t = FolderTypeReadWrite
+	case "readonly":
+		*t = FolderTypeReadOnly
+	default:
+		*t = FolderTypeReadWrite
+	}
+	return nil
+}