perf: avoid redundant Abs and Stat on directory walks

file_handling.go

@@ -14,6 +14,7 @@ import (
 type File struct {
 	Path string
 	info os.FileInfo
+	isDir *bool
 }
 
 // NewFile resolves path to an absolute path and wraps it in a *File. It
@@ -27,6 +28,16 @@ func NewFile(path string) (*File, error) {
 	return &File{Path: absPath}, nil
 }
 
+// NewChildFile joins name under an already-absolute parent without calling filepath.Abs again.
+func NewChildFile(parent *File, name string, entry os.DirEntry) *File {
+	child := &File{Path: filepath.Join(parent.Path, name)}
+	if entry != nil {
+		isDir := entry.IsDir()
+		child.isDir = &isDir
+	}
+	return child
+}
+
 func (f *File) Base() string {
 	return filepath.Base(f.Path)
 }
@@ -35,6 +46,18 @@ func (f *File) Dir() string {
 	return filepath.Dir(f.Path)
 }
 
+// IsDir reports whether f is a directory, using DirEntry metadata when available.
+func (f *File) IsDir() bool {
+	if f.isDir != nil {
+		return *f.isDir
+	}
+	info, err := f.Info()
+	if err != nil {
+		return false
+	}
+	return info.IsDir()
+}
+
 // Info lazily stats the file and caches the result. It returns an error if
 // the underlying os.Stat fails.
 func (f *File) Info() (os.FileInfo, error) {

file_handling_test.go

@@ -6,6 +6,20 @@ import (
 )
 
 // TestNewFile exercises NewFile's path-resolution behavior.
+
+func TestNewChildFile(t *testing.T) {
+	tmp := t.TempDir()
+	parent, err := NewFile(tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	child := NewChildFile(parent, "sub", nil)
+	want := filepath.Join(parent.Path, "sub")
+	if child.Path != want {
+		t.Fatalf("NewChildFile path = %q; want %q", child.Path, want)
+	}
+}
+
 func TestNewFile(t *testing.T) {
 	tmp := t.TempDir()
 

find_replace.go

@@ -123,14 +123,8 @@ func (fr *findReplace) WalkDir(f *File) {
 		return
 	}
 
-	for _, file := range files {
-		childPath := filepath.Join(f.Path, file.Name())
-		childFile, err := NewFile(childPath)
-		if err != nil {
-			log.Print(err)
-			fr.errs.add(err)
-			continue
-		}
+	for _, entry := range files {
+		childFile := NewChildFile(f, entry.Name(), entry)
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
@@ -151,13 +145,8 @@ func (fr *findReplace) WalkDir(f *File) {
 // the rename step; the failure is returned so the walker can log it and
 // continue with siblings.
 func (fr *findReplace) HandleFile(f *File) error {
-	info, err := f.Info()
-	if err != nil {
-		return err
-	}
-
 	// If file is a directory, recurse immediately (depth-first).
-	if info.IsDir() {
+	if f.IsDir() {
 		// Ignore certain directories
 		if f.Base() == ".git" {
 			return nil