R1:c408168c2500

Diffusion - Warn users to explicitly provide PATH for SVN hosted repositories

Summary: Fixes T4547.

Test Plan: saw the warning, looked good

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4547

Differential Revision: https://secure.phabricator.com/D8706