Allow inline comments to be individually hidden

Summary:
Ref T7447. Implements per-viewer comment hiding. Once a comment is obsolete or uninteresting, you can hide it completely.

This is sticky per-user.

My hope is that this will strike a better balance between concerns than some of the other approaches (conservative porting, summarization, hide-all).

Specifically, this adds a new action here:

{F435621}

Clicking it completely collapses the comment into a small icon on the previous line, and saves the comment state as hidden for you:

{F435626}

You can click the icon to reveal all hidden comments below the line.

Test Plan:
  - Hid comments.
  - Showed comments.
  - Created, edited, deleted and submitted comments.
  - Used Diffusion comments (hiding is not implemented there yet, but I'd plan to bring it there eventually if it works out in Differential).

Reviewers: btrahan, chad

Reviewed By: btrahan

Subscribers: jparise, yelirekim, epriestley

Maniphest Tasks: T7447

Differential Revision: https://secure.phabricator.com/D13009

src/applications/differential/query/DifferentialInlineCommentQuery.php

@@ -15,6 +15,7 @@ final class DifferentialInlineCommentQuery
   private $authorPHIDs;
   private $revisionPHIDs;
   private $deletedDrafts;
+  private $needHidden;
 
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
@@ -55,6 +56,11 @@ final class DifferentialInlineCommentQuery
     return $this;
   }
 
+  public function needHidden($need) {
+    $this->needHidden = $need;
+    return $this;
+  }
+
   public function execute() {
     $table = new DifferentialTransactionComment();
     $conn_r = $table->establishConnection('r');
@@ -68,6 +74,26 @@ final class DifferentialInlineCommentQuery
 
     $comments = $table->loadAllFromArray($data);
 
+    if ($this->needHidden) {
+      $viewer_phid = $this->getViewer()->getPHID();
+      if ($viewer_phid && $comments) {
+        $hidden = queryfx_all(
+          $conn_r,
+          'SELECT commentID FROM %T WHERE userPHID = %s
+            AND commentID IN (%Ls)',
+          id(new DifferentialHiddenComment())->getTableName(),
+          $viewer_phid,
+          mpull($comments, 'getID'));
+        $hidden = array_fuse(ipull($hidden, 'commentID'));
+      } else {
+        $hidden = array();
+      }
+
+      foreach ($comments as $inline) {
+        $inline->attachIsHidden(isset($hidden[$inline->getID()]));
+      }
+    }
+
     foreach ($comments as $key => $value) {
       $comments[$key] = DifferentialInlineComment::newFromModernComment(
         $value);