Log Message:
Changes 1.8.3.1:
 * When $HOME is misconfigured to point at an unreadable directory, we
   used to complain and die. The check has been loosened.
 * Handling of negative exclude pattern for directories "!dir" was
   broken in the update to v1.8.3.
Also contains a handful of trivial code clean-ups, documentation
updates, updates to the test suite, etc.