I had to remove the evaluation cache and parallel formatting for now in
order to make this manageable.

* Load the config
* Prepare for filesystem traversal
* Match each path against the formatters and collect the ones that
  match. Get the mtime from the traversal entry to avoid additional
  syscalls.
* Now that we have a map from formatter to paths, run each formatter
  against its list. Collect a list of new mtimes.
* Finally display the list of files that have changed.

This is already handled by the formatter himself