Port comments through time and space in the common/best case

Summary:
Ref T7447. This ports comments forward and backward in the best case:

  - The old comment is on a changeset with the same filename.
  - The old and new files are pretty much the same, line-for-line.

This will fail to port a lot of comments around and probably port a lot of comments into goofy places. We can see how bad it is in practice.

Errata:

  - Design is me cobbling something together, probably worth tweaking.
  - "Old Comment" should, at a minimum, say "Newer Comment" sometimes, or we should come up with some better name for this stuff.

Test Plan: {F377214}

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: johnny-bit, yelirekim, epriestley

Maniphest Tasks: T7447

Differential Revision: https://secure.phabricator.com/D12484

src/applications/differential/query/DifferentialInlineCommentQuery.php

@@ -13,7 +13,6 @@ final class DifferentialInlineCommentQuery
   private $phids;
   private $drafts;
   private $authorPHIDs;
-  private $changesetIDs;
   private $revisionPHIDs;
   private $deletedDrafts;
 
@@ -46,11 +45,6 @@ final class DifferentialInlineCommentQuery
     return $this;
   }
 
-  public function withChangesetIDs(array $ids) {
-    $this->changesetIDs = $ids;
-    return $this;
-  }
-
   public function withRevisionPHIDs(array $revision_phids) {
     $this->revisionPHIDs = $revision_phids;
     return $this;
@@ -116,13 +110,6 @@ final class DifferentialInlineCommentQuery
         $this->revisionPHIDs);
     }
 
-    if ($this->changesetIDs !== null) {
-      $where[] = qsprintf(
-        $conn_r,
-        'changesetID IN (%Ld)',
-        $this->changesetIDs);
-    }
-
     if ($this->drafts === null) {
       if ($this->deletedDrafts) {
         $where[] = qsprintf(