Add a basic push log for recording repository push events

Summary:
Ref T4195. This log serves two purposes:

  - It's a log, so you can see what happened. Particularly, in Git/Hg, there is no other way to tell:
    - Who //pushed// a change (vs committed / authored)?
    - When was a change pushed?
    - What was the old value of some tag/branch before someone destroyed it?
  - We can hand these objects off to Herald to implement pre-commit rules.

This is a very basic implementation, but gets some data written and has a basic UI for it.

Test Plan: {F87339}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4195

Differential Revision: https://secure.phabricator.com/D7705

src/applications/diffusion/application/PhabricatorApplicationDiffusion.php

@@ -46,6 +46,9 @@ final class PhabricatorApplicationDiffusion extends PhabricatorApplication {
         'new/' => 'DiffusionRepositoryNewController',
         '(?P<edit>create)/' => 'DiffusionRepositoryCreateController',
         '(?P<edit>import)/' => 'DiffusionRepositoryCreateController',
+        'pushlog/(?:query/(?P<queryKey>[^/]+)/)?'
+          => 'DiffusionPushLogListController',
+
         '(?P<callsign>[A-Z]+)/' => array(
           '' => 'DiffusionRepositoryController',
 
@@ -58,7 +61,6 @@ final class PhabricatorApplicationDiffusion extends PhabricatorApplication {
           'tags/(?P<dblob>.*)'          => 'DiffusionTagListController',
           'branches/(?P<dblob>.*)'      => 'DiffusionBranchTableController',
           'lint/(?P<dblob>.*)'          => 'DiffusionLintController',
-
           'commit/(?P<commit>[a-z0-9]+)/branches/'
             => 'DiffusionCommitBranchesController',
           'commit/(?P<commit>[a-z0-9]+)/tags/'