Add --restrict-library option

CHANGELOG

@@ -1,6 +1,6 @@
 0.1.3:
 - Allow keybindings to be configured
-- Add --fd option
+- Add --fd and --restrict-library options
 
 0.1.2:
 - Allow audio buffer size to be configured

gui.go

@@ -92,6 +92,16 @@ func browseFolder(browse string) {
 		mainBufferAutoFocus = ""
 		return
 	}
+	if !strings.HasPrefix(browse, restrictLibrary) {
+		statusText = "failed to browse folder: permission denied"
+		go func() {
+			time.Sleep(5 * time.Second)
+			statusText = ""
+			go app.QueueUpdateDraw(updateMain)
+		}()
+		go app.QueueUpdateDraw(updateMain)
+		return
+	}
 
 	placeCursorAtTop := mainBufferCursor == 0
 	mainBufferFiles = scanFolder(browse)

main.go

@@ -34,6 +34,7 @@ var (
 	cpuProfile       string
 	streamFdInt      int
 	streamFd         *os.File
+	restrictLibrary  string
 
 	done = make(chan bool)
 )
@@ -48,6 +49,7 @@ func main() {
 	flag.StringVar(&configPath, "config", "", "path to configuration file")
 	flag.BoolVar(&printVersionInfo, "version", false, "print version information and exit")
 	flag.IntVar(&streamFdInt, "fd", -1, "stream audio to file descriptor")
+	flag.StringVar(&restrictLibrary, "restrict-library", "", "restrict library to path")
 	flag.DurationVar(&bufferSize, "buffer-size", defaultBufferSize, "audio buffer size")
 	flag.StringVar(&debugAddress, "debug-address", "", "address to serve debug info")
 	flag.StringVar(&cpuProfile, "cpu-profile", "", "path to save CPU profiling")
@@ -58,6 +60,14 @@ func main() {
 		return
 	}
 
+	if restrictLibrary != "" {
+		var err error
+		restrictLibrary, err = filepath.Abs(restrictLibrary)
+		if err != nil {
+			log.Fatalf("failed to restrict library to %s: %s", restrictLibrary, err)
+		}
+	}
+
 	if debugAddress != "" {
 		go func() {
 			log.Fatal(http.ListenAndServe(debugAddress, nil))
@@ -113,14 +123,18 @@ func main() {
 
 	startPath := strings.Join(flag.Args(), " ")
 	if startPath == "" {
-		wd, err := os.Getwd()
-		if err != nil || wd == "" {
-			homeDir, err := os.UserHomeDir()
-			if err == nil && homeDir != "" {
-				startPath = homeDir
+		if restrictLibrary == "" {
+			wd, err := os.Getwd()
+			if err != nil || wd == "" {
+				homeDir, err := os.UserHomeDir()
+				if err == nil && homeDir != "" {
+					startPath = homeDir
+				}
+			} else {
+				startPath = wd
 			}
 		} else {
-			startPath = wd
+			startPath = restrictLibrary
 		}
 	}
 	if startPath == "" {