Add prune option to apply

main.go

@@ -33,7 +33,7 @@ func main() {
 	var err error
 	switch args[0] {
 	case "apply":
-		err = applyCmd()
+		err = applyCmd(args[1:])
 	case "add":
 		err = addCmd(args[1:])
 	case "help", "-h", "--help":
@@ -52,11 +52,20 @@ func main() {
 func usage() {
 	fmt.Println("sigil: minimal dotfile symlink manager")
 	fmt.Println("usage:")
-	fmt.Println("  sigil apply")
+	fmt.Println("  sigil apply [--prune]")
 	fmt.Println("  sigil add <path>")
 }
 
-func applyCmd() error {
+func applyCmd(args []string) error {
+	prune := false
+	for _, arg := range args {
+		if arg == "--prune" {
+			prune = true
+			continue
+		}
+		return fmt.Errorf("unknown flag %q", arg)
+	}
+
 	repo, err := repoPath()
 	if err != nil {
 		return err
@@ -67,6 +76,8 @@ func applyCmd() error {
 		return err
 	}
 
+	var stales []string
+
 	for _, entry := range entries {
 		if !entry.IsDir() || strings.HasPrefix(entry.Name(), ".") {
 			continue
@@ -102,6 +113,28 @@ func applyCmd() error {
 		if err := applyPackage(filesDir, targetRoot); err != nil {
 			return fmt.Errorf("%s: %w", entry.Name(), err)
 		}
+
+		stale, err := findStaleLinks(filesDir, targetRoot)
+		if err != nil {
+			return fmt.Errorf("%s: %w", entry.Name(), err)
+		}
+		stales = append(stales, stale...)
+	}
+
+	if len(stales) == 0 {
+		return nil
+	}
+
+	if prune {
+		return removeLinks(stales)
+	}
+
+	ok, err := promptYesNo("Found stale links. Prune them?", false)
+	if err != nil {
+		return err
+	}
+	if ok {
+		return removeLinks(stales)
 	}
 
 	return nil
@@ -395,6 +428,24 @@ func promptWithDefault(reader *bufio.Reader, label, def string) string {
 	return text
 }
 
+func promptYesNo(message string, def bool) (bool, error) {
+	reader := bufio.NewReader(os.Stdin)
+	defLabel := "y/N"
+	if def {
+		defLabel = "Y/n"
+	}
+	fmt.Printf("%s [%s]: ", message, defLabel)
+	text, err := reader.ReadString('\n')
+	if err != nil {
+		return false, err
+	}
+	text = strings.TrimSpace(strings.ToLower(text))
+	if text == "" {
+		return def, nil
+	}
+	return text == "y" || text == "yes", nil
+}
+
 func moveDirContents(srcDir, destDir string) error {
 	entries, err := os.ReadDir(srcDir)
 	if err != nil {
@@ -418,3 +469,57 @@ func moveDirContents(srcDir, destDir string) error {
 
 	return nil
 }
+
+func findStaleLinks(filesDir, targetRoot string) ([]string, error) {
+	known := make(map[string]struct{})
+
+	err := filepath.WalkDir(filesDir, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if path == filesDir || entry.IsDir() {
+			return nil
+		}
+		rel, err := filepath.Rel(filesDir, path)
+		if err != nil {
+			return err
+		}
+		known[filepath.Join(targetRoot, rel)] = struct{}{}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	var stale []string
+	for targetPath := range known {
+		info, err := os.Lstat(targetPath)
+		if errors.Is(err, os.ErrNotExist) {
+			continue
+		}
+		if err != nil {
+			return nil, err
+		}
+		if info.Mode()&os.ModeSymlink == 0 {
+			continue
+		}
+		src, err := os.Readlink(targetPath)
+		if err != nil {
+			return nil, err
+		}
+		if _, err := os.Stat(src); errors.Is(err, os.ErrNotExist) {
+			stale = append(stale, targetPath)
+		}
+	}
+
+	return stale, nil
+}
+
+func removeLinks(paths []string) error {
+	for _, path := range paths {
+		if err := os.Remove(path); err != nil {
+			return err
+		}
+	}
+	return nil
+}