misc/dist: include directories in distribution tar and zip files.

Fixes #3458.

R=adg, dsymonds
CC=golang-dev
https://golang.org/cl/5969071

misc/dist/bindist.go

@@ -574,9 +574,6 @@ func makeTar(targ, workdir string) error {
 		if *verbose {
 			log.Printf("adding to tar: %s", name)
 		}
-		if fi.IsDir() {
-			return nil
-		}
 		hdr, err := tarFileInfoHeader(fi, path)
 		if err != nil {
 			return err
@@ -598,6 +595,9 @@ func makeTar(targ, workdir string) error {
 		if err != nil {
 			return fmt.Errorf("Error writing file %q: %v", name, err)
 		}
+		if fi.IsDir() {
+			return nil
+		}
 		r, err := os.Open(path)
 		if err != nil {
 			return err
@@ -626,9 +626,6 @@ func makeZip(targ, workdir string) error {
 	zw := zip.NewWriter(f)
 
 	err = filepath.Walk(workdir, func(path string, fi os.FileInfo, err error) error {
-		if fi.IsDir() {
-			return nil
-		}
 		if !strings.HasPrefix(path, workdir) {
 			log.Panicf("walked filename %q doesn't begin with workdir %q", path, workdir)
 		}
@@ -655,10 +652,17 @@ func makeZip(targ, workdir string) error {
 		}
 		fh.Name = name
 		fh.Method = zip.Deflate
+		if fi.IsDir() {
+			fh.Name += "/"        // append trailing slash
+			fh.Method = zip.Store // no need to deflate 0 byte files
+		}
 		w, err := zw.CreateHeader(fh)
 		if err != nil {
 			return err
 		}
+		if fi.IsDir() {
+			return nil
+		}
 		r, err := os.Open(path)
 		if err != nil {
 			return err