Allow projects to be "watched", sort of a super-subscribe

Summary:
Ref T4967. Adds a "Watch" relationship to projects, which is stronger than member/subscribed.

Specifically, when a task is tagged with a project, we'll include all project watchers in the email/notifications. Normally we don't include projects unless they're explicitly CC'd, or have some other active role in the object (like being a reviewer or auditor).

This allows you to closely follow a project without needing to write a Herald rule for every project you care about.

Test Plan:
  - Watched/unwatched a project.
  - Tested the watch/subscribe/member relationships:
    - Watching implies subscribe.
    - Joining implies subscribe.
    - Leaving implies unsubscribe + unwatch.
    - You can't unsubscribe until you unwatch (slightly better would be unsubscribe implies unwatch, but this is a bit tricky).
  - Watched a project, then recevied email about a tagged task without otherwise being involved.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4967

Differential Revision: https://secure.phabricator.com/D9185

src/applications/project/controller/PhabricatorProjectWatchController.php

@@ -0,0 +1,97 @@
+<?php
+
+final class PhabricatorProjectWatchController
+  extends PhabricatorProjectController {
+
+  private $id;
+  private $action;
+
+  public function willProcessRequest(array $data) {
+    $this->id = $data['id'];
+    $this->action = $data['action'];
+  }
+
+  public function processRequest() {
+    $request = $this->getRequest();
+    $viewer = $request->getUser();
+
+    $project = id(new PhabricatorProjectQuery())
+      ->setViewer($viewer)
+      ->withIDs(array($this->id))
+      ->needMembers(true)
+      ->needWatchers(true)
+      ->executeOne();
+    if (!$project) {
+      return new Aphront404Response();
+    }
+
+    $project_uri = '/project/view/'.$project->getID().'/';
+
+    // You must be a member of a project to
+    if (!$project->isUserMember($viewer->getPHID())) {
+      return new Aphront400Response();
+    }
+
+    if ($request->isDialogFormPost()) {
+      $edge_action = null;
+      switch ($this->action) {
+        case 'watch':
+          $edge_action = '+';
+          $force_subscribe = true;
+          break;
+        case 'unwatch':
+          $edge_action = '-';
+          $force_subscribe = false;
+          break;
+      }
+
+      $type_member = PhabricatorEdgeConfig::TYPE_OBJECT_HAS_WATCHER;
+      $member_spec = array(
+        $edge_action => array($viewer->getPHID() => $viewer->getPHID()),
+      );
+
+      $xactions = array();
+      $xactions[] = id(new PhabricatorProjectTransaction())
+        ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
+        ->setMetadataValue('edge:type', $type_member)
+        ->setNewValue($member_spec);
+
+      $editor = id(new PhabricatorProjectTransactionEditor($project))
+        ->setActor($viewer)
+        ->setContentSourceFromRequest($request)
+        ->setContinueOnNoEffect(true)
+        ->setContinueOnMissingFields(true)
+        ->applyTransactions($project, $xactions);
+
+      return id(new AphrontRedirectResponse())->setURI($project_uri);
+    }
+
+    $dialog = null;
+    switch ($this->action) {
+      case 'watch':
+        $title = pht('Watch Project?');
+        $body = pht(
+          'Watching a project will let you monitor it closely. You will '.
+          'receive email and notifications about changes to every object '.
+          'associated with projects you watch.');
+        $submit = pht('Watch Project');
+        break;
+      case 'unwatch':
+        $title = pht('Unwatch Project?');
+        $body = pht(
+          'You will no longer receive email or notifications about every '.
+          'object associated with this project.');
+        $submit = pht('Unwatch Project');
+        break;
+      default:
+        return new Aphront404Response();
+    }
+
+    return $this->newDialog()
+      ->setTitle($title)
+      ->appendParagraph($body)
+      ->addCancelButton($project_uri)
+      ->addSubmitButton($submit);
+  }
+
+}