Add some Drydock documentation plus "Test Configuration" for repository automation

Summary:
Ref T182. Ref T9252.

  - Adds a "Test" repository operation that just runs `git status` to see if things work.
  - Adds a button for it in Edit Repository.
  - Shows operation status on the operation detail view to make this workflow work a little better.
  - Adds a lot of words. Words words words words.

Test Plan:
  - Tested repository operation.
  - Read words.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T182, T9252

Differential Revision: https://secure.phabricator.com/D14349

src/applications/diffusion/controller/DiffusionRepositoryEditAutomationController.php

@@ -4,7 +4,7 @@ final class DiffusionRepositoryEditAutomationController
   extends DiffusionRepositoryEditController {
 
   protected function processDiffusionRequest(AphrontRequest $request) {
-    $viewer = $request->getUser();
+    $viewer = $this->getViewer();
     $drequest = $this->diffusionRequest;
     $repository = $drequest->getRepository();