zipsync handles symlink

This change fixes a bug that zipsync didn't handle symlink correctly;
symlink was extracted as a regular file whose content is the target
path. Fixing the problem by correctly creating the symlink using
os.Symlink.

Bug: N/A
Test: manual

Change-Id: Ib6685c14e1950d1057d89672883cdd9e4879069a

cmd/zipsync/zipsync.go

@@ -53,6 +53,16 @@ func writeFile(filename string, in io.Reader, perm os.FileMode) error {
 	return out.Close()
 }
 
+func writeSymlink(filename string, in io.Reader) error {
+	b, err := ioutil.ReadAll(in)
+	if err != nil {
+		return err
+	}
+	dest := string(b)
+	err = os.Symlink(dest, filename)
+	return err
+}
+
 func main() {
 	flag.Usage = func() {
 		fmt.Fprintln(os.Stderr, "usage: zipsync -d <output dir> [-l <output file>] [-f <pattern>] [zip]...")
@@ -122,7 +132,11 @@ func main() {
 				if err != nil {
 					log.Fatal(err)
 				}
-				must(writeFile(filename, in, f.FileInfo().Mode()))
+				if f.FileInfo().Mode()&os.ModeSymlink != 0 {
+					must(writeSymlink(filename, in))
+				} else {
+					must(writeFile(filename, in, f.FileInfo().Mode()))
+				}
 				in.Close()
 				files = append(files, filename)
 			}