feat(file-ignore): apply exclude rules lazily

- apply exclude rules from filter when iterating over dir contents
 instead of at serialFile construction time

serialfile.go

@@ -58,7 +58,7 @@ func NewSerialFileWithFilter(path string, filter *Filter, stat os.FileInfo) (Nod
 		if err != nil {
 			return nil, err
 		}
-		return &serialFile{path, filterFiles(filter, contents), stat, filter}, nil
+		return &serialFile{path, contents, stat, filter}, nil
 	case mode&os.ModeSymlink != 0:
 		target, err := os.Readlink(path)
 		if err != nil {
@@ -86,7 +86,7 @@ func (it *serialIterator) Next() bool {
 
 	stat := it.files[0]
 	it.files = it.files[1:]
-	for !it.filter.IncludeHidden && isHidden(stat) {
+	for it.filter.ShouldExclude(stat) {
 		if len(it.files) == 0 {
 			return false
 		}
@@ -133,7 +133,7 @@ func (f *serialFile) NextFile() (string, Node, error) {
 	stat := f.files[0]
 	f.files = f.files[1:]
 
-	for !f.filter.IncludeHidden && isHidden(stat) {
+	for !f.filter.ShouldExclude(stat) {
 		if len(f.files) == 0 {
 			return "", nil, io.EOF
 		}
@@ -187,17 +187,3 @@ func (f *serialFile) Size() (int64, error) {
 
 var _ Directory = &serialFile{}
 var _ DirIterator = &serialIterator{}
-
-func filterFiles(filter *Filter, files []os.FileInfo) (res []os.FileInfo) {
-	for _, file := range files {
-		name := file.Name()
-		if file.IsDir() {
-			name = fmt.Sprintf("%s/", name)
-		}
-		if filter.ShouldExclude(file) {
-			continue
-		}
-		res = append(res, file)
-	}
-	return
-}