The handling  for 'directory' and 'filetree' can actually be done in the **MetacelloPharoPlatform** class (let's rename the class to **MetacelloPharo20Platform** to avoid potential confusion). 

That means we'd want to restore the FileDirectory references here ....If leaving the direct references to FileDirectory in this common method is problematic, then we can do `Smalltalk at: #FileDirectory`.