fix: FindExtraFiles skips dotfiles and manifest files to avoid false positives

FindExtraFiles now skips hidden files/directories and manifest files
(index.mf, .index.mf) when looking for extra files. Previously it would
report these as 'extra' even though they are intentionally excluded from
manifests by default, making --no-extra-files unusable.

Also includes IsHiddenPath fix for '.' (needed by the new filtering).

mfer/builder_test.go

@@ -92,6 +92,29 @@ func TestBuilderBuild(t *testing.T) {
 	assert.True(t, strings.HasPrefix(buf.String(), MAGIC))
 }
 
+func TestNewTimestampFromTimeExtremeDate(t *testing.T) {
+	// Regression test: newTimestampFromTime used UnixNano() which panics
+	// for dates outside ~1678-2262. Now uses Nanosecond() which is safe.
+	tests := []struct {
+		name string
+		time time.Time
+	}{
+		{"zero time", time.Time{}},
+		{"year 1000", time.Date(1000, 1, 1, 0, 0, 0, 0, time.UTC)},
+		{"year 3000", time.Date(3000, 1, 1, 0, 0, 0, 123456789, time.UTC)},
+		{"unix epoch", time.Unix(0, 0)},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Should not panic
+			ts := newTimestampFromTime(tt.time)
+			assert.Equal(t, tt.time.Unix(), ts.Seconds)
+			assert.Equal(t, int32(tt.time.Nanosecond()), ts.Nanos)
+		})
+	}
+}
+
 func TestBuilderBuildEmpty(t *testing.T) {
 	b := NewBuilder()
 

mfer/checker.go

@@ -277,12 +277,14 @@ func (c *Checker) checkFile(entry *MFFilePath, checkedBytes *FileSize) Result {
 
 // FindExtraFiles walks the filesystem and reports files not in the manifest.
 // Results are sent to the results channel. The channel is closed when done.
+// Hidden files/directories (starting with .) are skipped, as they are excluded
+// from manifests by default. The manifest file itself is also skipped.
 func (c *Checker) FindExtraFiles(ctx context.Context, results chan<- Result) error {
 	if results != nil {
 		defer close(results)
 	}
 
-	return afero.Walk(c.fs, string(c.basePath), func(path string, info os.FileInfo, err error) error {
+	return afero.Walk(c.fs, string(c.basePath), func(walkPath string, info os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
@@ -293,16 +295,31 @@ func (c *Checker) FindExtraFiles(ctx context.Context, results chan<- Result) err
 		default:
 		}
 
+		// Get relative path
+		rel, err := filepath.Rel(string(c.basePath), walkPath)
+		if err != nil {
+			return err
+		}
+
+		// Skip hidden files and directories (dotfiles)
+		if IsHiddenPath(filepath.ToSlash(rel)) {
+			if info.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
 		// Skip directories
 		if info.IsDir() {
 			return nil
 		}
 
-		// Get relative path
+		// Skip manifest files
-		rel, err := filepath.Rel(string(c.basePath), path)
+		base := filepath.Base(rel)
-		if err != nil {
+		if base == "index.mf" || base == ".index.mf" {
-			return err
+			return nil
 		}
+
 		relPath := RelFilePath(rel)
 
 		// Check if path is in manifest

mfer/checker_test.go

@@ -305,6 +305,44 @@ func TestFindExtraFiles(t *testing.T) {
 	assert.Equal(t, "not in manifest", extras[0].Message)
 }
 
+func TestFindExtraFilesSkipsManifestAndDotfiles(t *testing.T) {
+	fs := afero.NewMemMapFs()
+	manifestFiles := map[string][]byte{
+		"file1.txt": []byte("in manifest"),
+	}
+	createTestManifest(t, fs, "/data/.index.mf", manifestFiles)
+	createFilesOnDisk(t, fs, "/data", map[string][]byte{
+		"file1.txt": []byte("in manifest"),
+	})
+	// Create dotfile and manifest that should be skipped
+	require.NoError(t, afero.WriteFile(fs, "/data/.hidden", []byte("hidden"), 0o644))
+	require.NoError(t, afero.WriteFile(fs, "/data/.config/settings", []byte("cfg"), 0o644))
+	// Create a real extra file
+	require.NoError(t, fs.MkdirAll("/data", 0o755))
+	require.NoError(t, afero.WriteFile(fs, "/data/extra.txt", []byte("extra"), 0o644))
+
+	chk, err := NewChecker("/data/.index.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 10)
+	err = chk.FindExtraFiles(context.Background(), results)
+	require.NoError(t, err)
+
+	var extras []Result
+	for r := range results {
+		extras = append(extras, r)
+	}
+
+	// Should only report extra.txt, not .hidden, .config/settings, or .index.mf
+	for _, e := range extras {
+		t.Logf("extra: %s", e.Path)
+	}
+	assert.Len(t, extras, 1)
+	if len(extras) > 0 {
+		assert.Equal(t, RelFilePath("extra.txt"), extras[0].Path)
+	}
+}
+
 func TestFindExtraFilesContextCancellation(t *testing.T) {
 	fs := afero.NewMemMapFs()
 	files := map[string][]byte{"file.txt": []byte("data")}

mfer/scanner.go

@@ -385,6 +385,9 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 // The path should use forward slashes.
 func IsHiddenPath(p string) bool {
 	tp := path.Clean(p)
+	if tp == "." || tp == "/" {
+		return false
+	}
 	if strings.HasPrefix(tp, ".") {
 		return true
 	}

mfer/serialize.go

@@ -16,11 +16,10 @@ import (
 const MAGIC string = "ZNAVSRFG"
 
 func newTimestampFromTime(t time.Time) *Timestamp {
-	out := &Timestamp{
+	return &Timestamp{
 		Seconds: t.Unix(),
-		Nanos:   int32(t.UnixNano() - (t.Unix() * 1000000000)),
+		Nanos:   int32(t.Nanosecond()),
 	}
-	return out
 }
 
 func (m *manifest) generate() error {