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/PhabricatorProjectProfileController.php

@@ -21,6 +21,7 @@ final class PhabricatorProjectProfileController
       ->setViewer($user)
       ->withIDs(array($this->id))
       ->needMembers(true)
+      ->needWatchers(true)
       ->needImages(true)
       ->executeOne();
     if (!$project) {
@@ -222,14 +223,32 @@ final class PhabricatorProjectProfileController
         ->setIcon('fa-plus')
         ->setDisabled(!$can_join)
         ->setName(pht('Join Project'));
+      $view->addAction($action);
     } else {
       $action = id(new PhabricatorActionView())
         ->setWorkflow(true)
         ->setHref('/project/update/'.$project->getID().'/leave/')
         ->setIcon('fa-times')
         ->setName(pht('Leave Project...'));
+      $view->addAction($action);
+
+      if (!$project->isUserWatcher($viewer->getPHID())) {
+        $action = id(new PhabricatorActionView())
+          ->setWorkflow(true)
+          ->setHref('/project/watch/'.$project->getID().'/')
+          ->setIcon('fa-eye')
+          ->setName(pht('Watch Project'));
+        $view->addAction($action);
+      } else {
+        $action = id(new PhabricatorActionView())
+          ->setWorkflow(true)
+          ->setHref('/project/unwatch/'.$project->getID().'/')
+          ->setIcon('fa-eye-slash')
+          ->setName(pht('Unwatch Project'));
+        $view->addAction($action);
+      }
     }
-    $view->addAction($action);
+
 
     return $view;
   }
@@ -240,7 +259,10 @@ final class PhabricatorProjectProfileController
     $request = $this->getRequest();
     $viewer = $request->getUser();
 
-    $this->loadHandles($project->getMemberPHIDs());
+    $this->loadHandles(
+      array_merge(
+        $project->getMemberPHIDs(),
+        $project->getWatcherPHIDs()));
 
     $view = id(new PHUIPropertyListView())
       ->setUser($viewer)
@@ -250,8 +272,14 @@ final class PhabricatorProjectProfileController
     $view->addProperty(
       pht('Members'),
       $project->getMemberPHIDs()
-      ? $this->renderHandlesForPHIDs($project->getMemberPHIDs(), ',')
-      : phutil_tag('em', array(), pht('None')));
+        ? $this->renderHandlesForPHIDs($project->getMemberPHIDs(), ',')
+        : phutil_tag('em', array(), pht('None')));
+
+    $view->addProperty(
+      pht('Watchers'),
+      $project->getWatcherPHIDs()
+        ? $this->renderHandlesForPHIDs($project->getWatcherPHIDs(), ',')
+        : phutil_tag('em', array(), pht('None')));
 
     $field_list = PhabricatorCustomField::getObjectFields(
       $project,