R1:e6c82c099481

Fix an issue with generating browser URIs in an SVN repository

Summary: Fixes T11866. This got converted wrong when doing the `/source/` stuff.

Test Plan: Browsed the root directory of a Subversion repository in Diffusion.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11866

Differential Revision: https://secure.phabricator.com/D16860