Excluding directories from upload

[GregoryAveryWeir]

I know this is a hard problem, but I would like to be able to exclude directories from the upload while still allowing all types of files to be uploaded. I'm using a mimeTypes of [/.*/], but as there is not yet a standard for directory drag/drop/upload from browsers, I'd like to be able to exclude directories while still allowing the upload of e.g. files without extensions.

Is there a way to make this distinction?