lib/fs: The interface and basicfs

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3748

lib/fs/basicfs_symlink_unix.go

@@ -0,0 +1,43 @@
+// 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/.
+
+// +build !windows
+
+package fs
+
+import "os"
+
+var symlinksSupported = true
+
+func DisableSymlinks() {
+	symlinksSupported = false
+}
+
+func (BasicFilesystem) SymlinksSupported() bool {
+	return symlinksSupported
+}
+
+func (BasicFilesystem) CreateSymlink(name, target string, _ LinkTargetType) error {
+	return os.Symlink(target, name)
+}
+
+func (BasicFilesystem) ChangeSymlinkType(_ string, _ LinkTargetType) error {
+	return nil
+}
+
+func (BasicFilesystem) ReadSymlink(path string) (string, LinkTargetType, error) {
+	tt := LinkTargetUnknown
+	if stat, err := os.Stat(path); err == nil {
+		if stat.IsDir() {
+			tt = LinkTargetDirectory
+		} else {
+			tt = LinkTargetFile
+		}
+	}
+
+	path, err := os.Readlink(path)
+	return path, tt, err
+}