Display compatible inline comments (usually synthetic) on the same row

Summary:
This just looks silly:
{F8088, size=full}

It runs in O(N*N) but it's not a big deal because there are usually only few
comments per line.
I didn't implement it for images.

Test Plan:
View revision with compatible inline comments in two diffs.
View revision with different inline comments on same line in two diffs.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1570

src/applications/differential/parser/changeset/DifferentialChangesetParser.php

@@ -1394,10 +1394,21 @@ class DifferentialChangesetParser {
       if ($o_num && isset($old_comments[$o_num])) {
         foreach ($old_comments[$o_num] as $comment) {
           $xhp = $this->renderInlineComment($comment);
+          $new = '';
+          if ($n_num && isset($new_comments[$n_num])) {
+            foreach ($new_comments[$n_num] as $key => $new_comment) {
+              if ($comment->isCompatible($new_comment)) {
+                $new = $this->renderInlineComment($new_comment);
+                unset($new_comments[$n_num][$key]);
+              }
+            }
+          }
           $html[] =
             '<tr class="inline"><th /><td>'.
               $xhp.
-            '</td><th /><td /><td class="cov" /></tr>';
+            '</td><th /><td>'.
+              $new.
+            '</td><td class="cov" /></tr>';
         }
       }
       if ($n_num && isset($new_comments[$n_num])) {

src/applications/differential/storage/inlinecomment/DifferentialInlineComment.php

@@ -42,4 +42,11 @@ class DifferentialInlineComment extends DifferentialDAO {
     return $this->syntheticAuthor;
   }
 
+  public function isCompatible(DifferentialInlineComment $comment) {
+    return
+      $this->authorPHID === $comment->authorPHID &&
+      $this->syntheticAuthor === $comment->syntheticAuthor &&
+      $this->content === $comment->content;
+  }
+
 }