Summary: Ref T13662. I ran into this while trying to reproduce the mention issue discussed there. Currently, the root document (with slug "/") attempts to preview using the URI `/phriction/preview//` (with two `//` at the end). This is collapsed into "/phriction/preview/" by Apache if "MergeSlashes On" is configured, which is the default behavior. The route then 404s. Instead, just use "/phriction/preview/?slug=/" so this endpoint functions properly regardless of the "MergeSlashes" configuration. Test Plan: - Configured Apache with "MergeSlashes On" (which is the default behavior). - Tried to preview a content edit of the root document in Phriction, which didn't work and generated 404s for "/phriction/preview//" in the console log. - Applied patch. - Previwed content in Phriction (which now worked properly). - Accessed `/a//b///c////` and similar with "MergeSlashes On" and "MergeSlashes Off", confirmed that this option controls whether PHP receives a URI with or without merged slashes in "__path__" after rewriting. Reviewers: 0 Reviewed By: 0 Maniphest Tasks: T13662 Differential Revision: https://secure.phabricator.com/D21708