Fix a missing setViewer() in differential.getrevision

Summary: DiffQuery now requires this.

Auditors: btrahan
Fix an issue with Diffusion where paging by commit date would fail

Summary: When loading the cursor repository, we need to load the most recent
commit too if we're paging by commit date. This fixes a fatal for installs
with more than 100 repositories.

Auditors: btrahan
Fix assign-on-close behavior for comment controller

Summary: Ref T2217. Missed this while converting this endpoint.

Test Plan: Closed an unassigned task, got assigned.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7089
Fix generation of "branch" URIs in Subversion repositories

Summary:
"Branch" really means "repository main screen, with some branch selected", so a branch isn't actually required since we can just take you to the default.

Fixes an issue where new crumbs would throw an exception in SVN repositories.

Test Plan: Browed an SVN repo.

Reviewers: btrahan, mbishopim3

Reviewed By: mbishopim3

CC: aran

Differential Revision: https://secure.phabricator.com/D7099