godoc: don't try to follow all symlinks

Revert https://golang.org/cl/45096.

Original change description:
    godoc: follow symbolic links to folders in GOROOT

    Directory walking in godoc relies on ReadDir which returns the result
    of os.Lstat.

    Instead make the the OS VFS's ReadDir use os.Stat on symlinks before
    returning.

Updates golang/go#15049
Fixes golang/go#21061

Change-Id: Ieaa7923d85842f3da5696a7f46134d16407dae66
Reviewed-on: https://go-review.googlesource.com/53634
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

godoc/vfs/os.go

@@ -7,11 +7,9 @@ package vfs
 import (
 	"fmt"
 	"io/ioutil"
-	"log"
 	"os"
 	pathpkg "path"
 	"path/filepath"
-	"strings"
 )
 
 // OS returns an implementation of FileSystem reading from the
@@ -59,35 +57,9 @@ func (root osFS) Lstat(path string) (os.FileInfo, error) {
 }
 
 func (root osFS) Stat(path string) (os.FileInfo, error) {
-	return stat(root.resolve(path))
+	return os.Stat(root.resolve(path))
 }
 
-var readdir = ioutil.ReadDir // for testing
-var stat = os.Stat           // for testing
-
 func (root osFS) ReadDir(path string) ([]os.FileInfo, error) {
-	fis, err := readdir(root.resolve(path))
-	if err != nil {
-		return fis, err
-	}
-	ret := fis[:0]
-
-	// reread the files with os.Stat since they might be symbolic links
-	for _, fi := range fis {
-		if fi.Mode()&os.ModeSymlink != 0 {
-			baseName := fi.Name()
-			fi, err = root.Stat(pathpkg.Join(path, baseName))
-			if err != nil {
-				if os.IsNotExist(err) && strings.HasPrefix(baseName, ".") {
-					// Ignore editor spam files without log spam.
-					continue
-				}
-				log.Printf("ignoring symlink: %v", err)
-				continue
-			}
-		}
-		ret = append(ret, fi)
-	}
-
-	return ret, nil // is sorted
+	return ioutil.ReadDir(root.resolve(path)) // is sorted
 }