Fix a dirname() edge case in Diffusion

Summary:
dirname('x') returns '.', not '/'; this caused some issues for repositories with
files at the root.

There are some cases in the parsers where I should probably swap this out too
but I'll wait until I'm doing some more rigorous testing since that stuff is a
bit fragile and this fixes an immediate issue.

Test Plan: Ran unit tests. Viewed a file at root level in a test repository.

Reviewers: jungejason, nh, tuomaspelkonen, aran

Reviewed By: nh

CC: aran, nh

Differential Revision: 932

src/__phutil_library_map__.php

@@ -262,6 +262,7 @@ phutil_register_library_map(array(
     'DiffusionPathChangeQuery' => 'applications/diffusion/query/pathchange/base',
     'DiffusionPathCompleteController' => 'applications/diffusion/controller/pathcomplete',
     'DiffusionPathIDQuery' => 'applications/diffusion/query/pathid/base',
+    'DiffusionPathQueryTestCase' => 'applications/diffusion/query/pathid/base/__tests__',
     'DiffusionPathValidateController' => 'applications/diffusion/controller/pathvalidate',
     'DiffusionRepositoryController' => 'applications/diffusion/controller/repository',
     'DiffusionRepositoryPath' => 'applications/diffusion/data/repositorypath',
@@ -918,6 +919,7 @@ phutil_register_library_map(array(
     'DiffusionHomeController' => 'DiffusionController',
     'DiffusionLastModifiedController' => 'DiffusionController',
     'DiffusionPathCompleteController' => 'DiffusionController',
+    'DiffusionPathQueryTestCase' => 'PhabricatorTestCase',
     'DiffusionPathValidateController' => 'DiffusionController',
     'DiffusionRepositoryController' => 'DiffusionController',
     'DiffusionSvnBrowseQuery' => 'DiffusionBrowseQuery',