Log changed files after backup

internal/restic/restic.go

@@ -98,6 +98,16 @@ type Stats struct {
 	TotalBlobCount int64 `json:"total_blob_count"`
 }
 
+type DiffEntry struct {
+	Kind string
+	Path string
+}
+
+type DiffResult struct {
+	Entries []DiffEntry
+	Total   int
+}
+
 func (r *Runner) Init(ctx context.Context, repo model.Repository) error {
 	return r.run(ctx, repo, []string{"init"}, nil, nil)
 }
@@ -280,6 +290,58 @@ func (r *Runner) List(ctx context.Context, repo model.Repository, snapshot, path
 	return items, scanner.Err()
 }
 
+func (r *Runner) Diff(ctx context.Context, repo model.Repository, before, after string, limit int) (DiffResult, error) {
+	var output []byte
+	if err := r.run(ctx, repo, []string{"diff", "--metadata", before, after}, nil, &output); err != nil {
+		return DiffResult{}, err
+	}
+	return parseDiffOutput(output, limit), nil
+}
+
+func parseDiffOutput(output []byte, limit int) DiffResult {
+	if limit <= 0 {
+		limit = 50
+	}
+	result := DiffResult{}
+	scanner := bufio.NewScanner(bytes.NewReader(output))
+	scanner.Buffer(make([]byte, 0, 64*1024), 2*1024*1024)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) < 2 {
+			continue
+		}
+		kind := diffKind(line[0])
+		if kind == "" {
+			continue
+		}
+		path := strings.TrimSpace(line[1:])
+		if path == "" || !strings.HasPrefix(path, "/") {
+			continue
+		}
+		result.Total++
+		if len(result.Entries) == limit {
+			copy(result.Entries, result.Entries[1:])
+			result.Entries[len(result.Entries)-1] = DiffEntry{Kind: kind, Path: path}
+			continue
+		}
+		result.Entries = append(result.Entries, DiffEntry{Kind: kind, Path: path})
+	}
+	return result
+}
+
+func diffKind(marker byte) string {
+	switch marker {
+	case '+':
+		return "new"
+	case '-':
+		return "removed"
+	case 'M':
+		return "modified"
+	default:
+		return ""
+	}
+}
+
 func (r *Runner) Restore(ctx context.Context, repo model.Repository, task model.RestoreTask, progress ProgressCallback) error {
 	args := []string{"restore", task.SnapshotID, "--target", task.Target, "--json"}
 	for _, include := range task.Includes {