Land to GitHub + support stuff

Summary:
A usable, Land to GitHub flow.

Still to do:
- Refactor all git/hg stratagies to a sane structure.
- Make the dialogs Workflow + explain why it's disabled.
- Show button and request Link Account if GH is enabled, but user is not linked.
- After refreshing token, user ends up in the settings stage.

Hacked something in LandController to be able to show an arbitrary dialog from a strategy.
It's not very nice, but I want to make some more refactoring to the controller/strategy/ies anyway.

Also made PhabricatorRepository::getRemoteURIObject() public, because it was very useful in getting
the domain and path for the repo.

Test Plan:
Went through these flows:
- load revision in hosted, github-backed, non-github backed repos to see button as needed.
- hit land with weak token - sent to refresh it with the extra scope.
- Land to repo I'm not allowed - got proper error message.
- Successfully landed; Failed to apply patch.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T182

Differential Revision: https://secure.phabricator.com/D7555

src/applications/differential/controller/DifferentialRevisionLandController.php

@@ -36,13 +36,14 @@ final class DifferentialRevisionLandController extends DifferentialController {
     }
 
     if ($request->isDialogFormPost()) {
+      $response = null;
+      $text = '';
       try {
-        $this->attemptLand($revision, $request);
+        $response = $this->attemptLand($revision, $request);
         $title = pht("Success!");
         $text = pht("Revision was successfully landed.");
       } catch (Exception $ex) {
         $title = pht("Failed to land revision");
-        $text = 'moo';
         if ($ex instanceof PhutilProxyException) {
           $text = hsprintf(
             '%s:<br><pre>%s</pre>',
@@ -55,13 +56,15 @@ final class DifferentialRevisionLandController extends DifferentialController {
            ->appendChild($text);
       }
 
-      $dialog = id(new AphrontDialogView())
-        ->setUser($viewer)
-        ->setTitle($title)
-        ->appendChild(phutil_tag('p', array(), $text))
-        ->setSubmitURI('/D'.$revision_id)
-        ->addSubmitButton(pht('Done'));
-
+      if ($response instanceof AphrontDialogView) {
+        $dialog = $response;
+      } else {
+        $dialog = id(new AphrontDialogView())
+          ->setUser($viewer)
+          ->setTitle($title)
+          ->appendChild(phutil_tag('p', array(), $text))
+          ->addCancelButton('/D'.$revision_id, pht('Done'));
+      }
       return id(new AphrontDialogResponse())->setDialog($dialog);
     }
 
@@ -108,7 +111,7 @@ final class DifferentialRevisionLandController extends DifferentialController {
     $lock = $this->lockRepository($repository);
 
     try {
-      $this->pushStrategy->processLandRequest(
+      $response = $this->pushStrategy->processLandRequest(
         $request,
         $revision,
         $repository);
@@ -118,6 +121,7 @@ final class DifferentialRevisionLandController extends DifferentialController {
     }
 
     $lock->unlock();
+    return $response;
   }
 
   private function lockRepository($repository) {