all: Convert folders to use filesystem abstraction

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4228

lib/fs/util.go

@@ -0,0 +1,55 @@
+// 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 https://mozilla.org/MPL/2.0/.
+
+package fs
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+var errNoHome = errors.New("no home directory found - set $HOME (or the platform equivalent)")
+
+func ExpandTilde(path string) (string, error) {
+	if path == "~" {
+		return getHomeDir()
+	}
+
+	path = filepath.FromSlash(path)
+	if !strings.HasPrefix(path, fmt.Sprintf("~%c", PathSeparator)) {
+		return path, nil
+	}
+
+	home, err := getHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, path[2:]), nil
+}
+
+func getHomeDir() (string, error) {
+	var home string
+
+	switch runtime.GOOS {
+	case "windows":
+		home = filepath.Join(os.Getenv("HomeDrive"), os.Getenv("HomePath"))
+		if home == "" {
+			home = os.Getenv("UserProfile")
+		}
+	default:
+		home = os.Getenv("HOME")
+	}
+
+	if home == "" {
+		return "", errNoHome
+	}
+
+	return home, nil
+}