R1:a316a0bbb38b

Define DiffusionRequest::setPath()

Summary: Resolves T2056.

Test Plan: Browsed SVN repo.

Reviewers: epriestley

Reviewed By: epriestley

CC: ced, aran, Korvin

Maniphest Tasks: T2056

Differential Revision: https://secure.phabricator.com/D3943