Make subproject/milestone watch rules work better

Summary:
Ref T10349. These got sort of half-weirded-up before I separated subscriptions and watching fully. New rules are:

  - You can watch whatever you want.
  - Watching a parent watches everything inside it.
  - If you're watching "Stonework" and go to "Stonework > Masonry", you'll see a "Watching Ancestor" hint to let you know you're already watching a parent or ancestor.

Test Plan:
  - Watched and unwatched "Stonework".
  - Watched and unwatched "Stonework > Iteration IV".
  - While watching "Stonework", visited "Iteration IV" and saw "Watching Ancestor" hint.
  - Created a task tagged "Stonework > Iteration IV". Got notified about it because I watch "Stonework".

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10349

Differential Revision: https://secure.phabricator.com/D15280

src/applications/project/controller/PhabricatorProjectProfileController.php

@@ -162,19 +162,32 @@ final class PhabricatorProjectProfileController
 
   private function renderWatchAction(PhabricatorProject $project) {
     $viewer = $this->getViewer();
-    $viewer_phid = $viewer->getPHID();
     $id = $project->getID();
 
-    $is_watcher = ($viewer_phid && $project->isUserWatcher($viewer_phid));
+    if (!$viewer->isLoggedIn()) {
+      $is_watcher = false;
+      $is_ancestor = false;
+    } else {
+      $viewer_phid = $viewer->getPHID();
+      $is_watcher = $project->isUserWatcher($viewer_phid);
+      $is_ancestor = $project->isUserAncestorWatcher($viewer_phid);
+    }
 
-    if (!$is_watcher) {
+    if ($is_ancestor && !$is_watcher) {
+      $watch_icon = 'fa-eye';
+      $watch_text = pht('Watching Ancestor');
+      $watch_href = "/project/watch/{$id}/?via=profile";
+      $watch_disabled = true;
+    } else if (!$is_watcher) {
       $watch_icon = 'fa-eye';
       $watch_text = pht('Watch Project');
       $watch_href = "/project/watch/{$id}/?via=profile";
+      $watch_disabled = false;
     } else {
       $watch_icon = 'fa-eye-slash';
       $watch_text = pht('Unwatch Project');
       $watch_href = "/project/unwatch/{$id}/?via=profile";
+      $watch_disabled = false;
     }
 
     $watch_icon = id(new PHUIIconView())
@@ -185,7 +198,8 @@ final class PhabricatorProjectProfileController
       ->setWorkflow(true)
       ->setIcon($watch_icon)
       ->setText($watch_text)
-      ->setHref($watch_href);
+      ->setHref($watch_href)
+      ->setDisabled($watch_disabled);
   }
 
   private function buildMilestoneList(PhabricatorProject $project) {