// factor this function out into a package to reduce duplication.
func overlayDir(dstRoot, srcRoot string) error {
	dstRoot = filepath.Clean(dstRoot)
	if err := os.MkdirAll(dstRoot, 0777); err != nil {
		return err
	}

	srcRoot, err := filepath.Abs(srcRoot)
	if err != nil {
		return err
	}

	return filepath.WalkDir(srcRoot, func(srcPath string, entry fs.DirEntry, err error) error {

	}
	defer robustio.RemoveAll(tmp)

	file := filepath.Join(tmp, "a.go")
	err = os.WriteFile(file, []byte{}, 0644)
	if err != nil {
		t.Fatal(err)
	}
	dir := filepath.Join(tmp, "dir")
	err = os.Mkdir(dir, 0777)
	if err != nil {
		t.Fatal(err)
	}

	noVolume := file[len(filepath.VolumeName(file)):]
	wrongPath := filepath.Join(dir, noVolume)
	cmd := testenv.Command(t, tg.goTool(), "build", noVolume)
	cmd.Dir = dir

			scriptfilename = "script.bat"
		}
		var cmd *exec.Cmd
		if runtime.GOOS == "windows" {
			scriptfile := filepath.Join(t.TempDir(), scriptfilename)
			if err := os.WriteFile(scriptfile, b.Bytes(), 0777); err != nil {
				t.Fatal(err)
			}
			cmd = testenv.Command(t, "cmd.exe", "/C", scriptfile)
		} else {
			cmd = testenv.Command(t, "sh", "-c", b.String())
		}
		out, err := cmd.Output()
		t.Log(string(out))

const bitSize16 = 2

func fileInfoFromStat(d *syscall.Dir) *fileStat {
	fs := &fileStat{
		name:    d.Name,
		size:    d.Length,
		modTime: time.Unix(int64(d.Mtime), 0),
		sys:     d,
	}
	fs.mode = FileMode(d.Mode & 0777)
	if d.Mode&syscall.DMDIR != 0 {
		fs.mode |= ModeDir
	}
	if d.Mode&syscall.DMAPPEND != 0 {
		fs.mode |= ModeAppend
	}
	if d.Mode&syscall.DMEXCL != 0 {
		fs.mode |= ModeExclusive
	}

	if err != nil {
		err = msgp.WrapError(err, "LimitInBytesPerSecond")
		return
	}
	// write "CurrentBandwidthInBytesPerSecond"
	err = en.Append(0xd9, 0x20, 0x43, 0x75, 0x72, 0x72, 0x65, 0x6e, 0x74, 0x42, 0x61, 0x6e, 0x64, 0x77, 0x69, 0x64, 0x74, 0x68, 0x49, 0x6e, 0x42, 0x79, 0x74, 0x65, 0x73, 0x50, 0x65, 0x72, 0x53, 0x65, 0x63, 0x6f, 0x6e, 0x64)
	if err != nil {
		return
	}
	err = en.WriteFloat64(z.CurrentBandwidthInBytesPerSecond)

	}
}

func TestDirAndSymlinkStats(t *testing.T) {
	testenv.MustHaveSymlink(t)
	t.Parallel()

	tmpdir := t.TempDir()
	dir := filepath.Join(tmpdir, "dir")
	if err := os.Mkdir(dir, 0777); err != nil {
		t.Fatal(err)
	}
	testDirStats(t, dir)

	dirlink := filepath.Join(tmpdir, "link")
	if err := os.Symlink(dir, dirlink); err != nil {
		t.Fatal(err)
	}
	testSymlinkStats(t, dirlink, true)

>>> Flow 1 (client to server)
00000000  16 03 01 00 39 01 00 00  35 03 01 eb 78 34 78 f6  |....9...5...x4x.|
00000010  8f 87 2f ee 5e da ee 37  5d 0a d5 79 d5 0e db b1  |../.^..7]..y....|
00000020  b7 03 37 1f 2d ce 04 b9  2d 65 d7 00 00 04 00 05  |..7.-...-e......|
00000030  00 ff 01 00 00 08 00 16  00 00 00 17 00 00        |..............|
>>> Flow 2 (server to client)
00000000  16 03 01 00 35 02 00 00  31 03 01 00 00 00 00 00  |....5...1.......|

func genAuxMeta(t *testing.T, dstdir string) (string, string) {
	// Do a GOCOVERDIR=<tmp> go run hello.go
	src := filepath.Join(dstdir, "hello.go")
	if err := os.WriteFile(src, []byte(hellogo), 0777); err != nil {
		t.Fatalf("write failed: %v", err)
	}
	args := []string{"run", "-covermode=" + testing.CoverMode(), src}
	cmd := exec.Command(testenv.GoToolPath(t), args...)

00000290  73 bb b3 43 77 8d 0c 1c  f1 0f a1 d8 40 83 61 c9  |s..Cw.......@.a.|
000002a0  4c 72 2b 9d ae db 46 06  06 4d f4 c1 b3 3e c0 d1  |Lr+...F..M...>..|
000002b0  bd 42 d4 db fe 3d 13 60  84 5c 21 d3 3b e9 fa e7  |.B...=.`.\!.;...|
000002c0  16 03 03 00 ac 0c 00 00  a8 03 00 1d 20 ca 74 42  |............ .tB|
000002d0  03 67 f2 31 ac 68 dd 2c  db 23 7d 2c 84 df e9 50  |.g.1.h.,.#},...P|

	"strings"
)

// OverlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
func OverlayDir(dstRoot, srcRoot string) error {
	dstRoot = filepath.Clean(dstRoot)
	if err := os.MkdirAll(dstRoot, 0777); err != nil {
		return err
	}

	srcRoot, err := filepath.Abs(srcRoot)
	if err != nil {
		return err
	}

	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {