When a text keyword is present, sort by relevancy by default

E.g. when you're at http://drupal.org/project/modules if you enter text in the "Search modules" block and submit, it should remove any active (or default) sorts, and sort by relevancy by default. If you then select a different sort order, it should work (and preserve the text search). Two parts:

A) the logic to actually ignore/reset filters when you submit a text search

B) the logic to add a dummy "Relevancy" option in the sort block whenever there's text search. this would be selected by default when you submit the text in step A.