Reuse blacklisting code in exp_archive.

client/archiver/directory.go

Index: client/archiver/directory.go
diff --git a/client/archiver/directory.go b/client/archiver/directory.go
index ecb38d06d66afea03458da29c0f791d158b7b487..26e78882236b7fa1637c154942fa87aa9c4044d7 100644
--- a/client/archiver/directory.go
+++ b/client/archiver/directory.go
@@ -74,7 +74,7 @@ func walk(root string, fsView common.FilesystemView, c chan<- *walkItem) {
 		}
 
 		if relPath == "" { // empty string indicates skip.
-			return returnSkip(info)
+			return common.WalkFuncSkipFile(info)
 		}
 
 		if !info.IsDir() {
@@ -90,15 +90,6 @@ func walk(root string, fsView common.FilesystemView, c chan<- *walkItem) {
 
 }
 
-// returnSkip returns the return value expected from a filepath.WalkFunc in the case where no more processing of file should occur.
-func returnSkip(file os.FileInfo) error {
-	if file.IsDir() {
-		// Must not return io.SkipDir for file, filepath.walk() handles this badly.
-		return filepath.SkipDir
-	}
-	return nil
-}
-
 // PushDirectory walks a directory at root and creates a .isolated file.
 //
 // It walks the directories synchronously, then returns a *Item to signal when