I would like to use JFileChooser to do the following:

* Make all directories navigable
* Make only some files/directories acceptable (via
the accept() method of FileFilter)

Currently, this is impossible without overriding some swing code.
For example, BasicDirectoryModel calls accept() on all files, before
asking directories whether they are traversable. So, a directory
cannot be traversable and unacceptable.

This would make the file chooser much more useful!