Merge pull request #408 from wking/unspecified-attributes-for-initial-layer-base-2

manifest: Explicitly unspecified attributes for the initial layer directory

Author: vbatts

manifest.md

@@ -45,6 +45,7 @@ Unlike the [Manifest List](manifest-list.md), which contains information about a
     The array MUST have the base image at index 0.
     Subsequent layers MUST then follow in stack order (i.e. from `layers[0]` to `layers[len(layers)-1]`).
     The final filesystem layout MUST match the result of [applying](layer.md#applying) the layers to an empty directory.
+    The [ownership, mode, and other attributes](layer.md#file-attributes) of the initial empty directory are unspecified.
 
     Beyond the [descriptor requirements](descriptor.md#properties), the value has the following additional restrictions: