Add a small note to a TODO.

utils/pub/io.dart

Index: utils/pub/io.dart
diff --git a/utils/pub/io.dart b/utils/pub/io.dart
index ab0b1efe892a198c497f6c59a7b4e7f3d53242eb..8b53575ac7c1fe08d53985ffb65f95955f59b9b2 100644
--- a/utils/pub/io.dart
+++ b/utils/pub/io.dart
@@ -272,7 +272,9 @@ Future<List<String>> listDir(dir,
       file = join(dir, basename(file));
       contents.add(file);
 
-      // TODO(nweiz): don't manually recurse once issue 7358 is fixed.
+      // TODO(nweiz): don't manually recurse once issue 7358 is fixed. Note that
+      // once we remove the manual recursion, we'll need to explicitly filter
+      // out files in hidden directories.
       if (recursive) {
         children.add(doList(new Directory(file), listedDirectories));
       }