Recognize remarkup custom fields as remarkup blocks

Summary:
Fixes T5916. Key insight here is that the screenshot shows a custom "Detail Solution / Notes" field, which is why this mojo doesn't work: custom remarkup fields don't emit their content for mention/file extraction.

Also fix a bug where multiple blocks with file PHIDs could be merged improperly, discarding some file PHIDs.

Test Plan: Added a custom remarkup field, added files to it, saw them attach to the task when changes were saved.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5916

Differential Revision: https://secure.phabricator.com/D10335

Author: epriestley

src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php

@@ -19,6 +19,13 @@ public function getStyleForPropertyView() {
     return 'block';
   }
 
+  public function getApplicationTransactionRemarkupBlocks(
+    PhabricatorApplicationTransaction $xaction) {
+    return array(
+      $xaction->getNewValue(),
+    );
+  }
+
   public function renderPropertyViewValue(array $handles) {
     $value = $this->getFieldValue();
 

src/infrastructure/markup/PhabricatorMarkupEngine.php

@@ -530,13 +530,15 @@ public static function extractFilePHIDsFromEmbeddedFiles(
 
     foreach ($content_blocks as $content_block) {
       $engine->markupText($content_block);
-      $ids = $engine->getTextMetadata(
+      $phids = $engine->getTextMetadata(
         PhabricatorEmbedFileRemarkupRule::KEY_EMBED_FILE_PHIDS,
         array());
-      $files += $ids;
+      foreach ($phids as $phid) {
+        $files[$phid] = $phid;
+      }
     }
 
-    return $files;
+    return array_values($files);
   }
 
   /**