Unbreak regex filename search

Summary:
D9087 adds a nice typeahead but breaks the existing regex
search by quoting the pattern. Ideally, this change won't break the
typeahead, which as far as I can tell doesn't use the pattern
argument.

Test Plan:
Not yet.
RFC as to whether this change makes sense, will fix my local setup and resend if so.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15500