Make X-Herald-Rules header sticky

Summary:
This isn't terribly elegant but it solves the problem without loss of
generality. We can pursue a more finessed solution later if it seems prudent.

Test Plan:
Created a revision matched by a blanket herald rule, and then commented on it.
Comment email had X-Herald-Rules header in it.

Reviewed By: aran
Reviewers: aran, tuomaspelkonen, jungejason
CC: aran
Differential Revision: 218

resources/sql/patches/034.savedheader.sql

@@ -0,0 +1,4 @@
+CREATE TABLE phabricator_herald.herald_savedheader (
+  phid varchar(64) binary not null primary key,
+  header varchar(255) not null
+) ENGINE=InnoDB;

src/applications/differential/editor/comment/DifferentialCommentEditor.php

@@ -304,6 +304,9 @@ class DifferentialCommentEditor {
       ->loadHandles();
     $actor_handle = $handles[$this->actorPHID];
 
+    $xherald_header = HeraldTranscript::loadXHeraldRulesHeader(
+      $revision->getPHID());
+
     id(new DifferentialCommentMail(
       $revision,
       $actor_handle,
@@ -316,6 +319,7 @@ class DifferentialCommentEditor {
           array($revision->getAuthorPHID())))
       ->setCCPHIDs($revision->getCCPHIDs())
       ->setChangedByCommit($this->getChangedByCommit())
+      ->setXHeraldRulesHeader($xherald_header)
       ->send();
 
     $event_data = array(

src/applications/differential/editor/comment/__init__.php

@@ -13,6 +13,7 @@ phutil_require_module('phabricator', 'applications/differential/mail/comment');
 phutil_require_module('phabricator', 'applications/differential/storage/changeset');
 phutil_require_module('phabricator', 'applications/differential/storage/comment');
 phutil_require_module('phabricator', 'applications/differential/storage/inlinecomment');
+phutil_require_module('phabricator', 'applications/herald/storage/transcript/base');
 phutil_require_module('phabricator', 'applications/phid/handle/data');
 phutil_require_module('phabricator', 'infrastructure/daemon/timeline/storage/event');
 

src/applications/differential/editor/revision/DifferentialRevisionEditor.php

@@ -212,6 +212,10 @@ class DifferentialRevisionEditor {
       $xscript_phid = $xscript->getPHID();
       $xscript_header = $xscript->getXHeraldRulesHeader();
 
+      HeraldTranscript::saveXHeraldRulesHeader(
+        $revision->getPHID(),
+        $xscript_header);
+
       $sub = array(
         'rev' => array(),
         'ccs' => $adapter->getCCsAddedByHerald(),

src/applications/differential/editor/revision/__init__.php

@@ -13,6 +13,7 @@ phutil_require_module('phabricator', 'applications/differential/storage/comment'
 phutil_require_module('phabricator', 'applications/differential/storage/revision');
 phutil_require_module('phabricator', 'applications/herald/adapter/differential');
 phutil_require_module('phabricator', 'applications/herald/engine/engine');
+phutil_require_module('phabricator', 'applications/herald/storage/transcript/base');
 phutil_require_module('phabricator', 'applications/phid/handle/data');
 phutil_require_module('phabricator', 'applications/search/index/indexer/differential');
 phutil_require_module('phabricator', 'infrastructure/env');

src/applications/herald/storage/transcript/base/HeraldTranscript.php

@@ -33,6 +33,8 @@ class HeraldTranscript extends HeraldDAO {
   protected $objectPHID;
   protected $dryRun;
 
+  const TABLE_SAVED_HEADER = 'herald_savedheader';
+
   public function getXHeraldRulesHeader() {
     $ids = array();
     foreach ($this->applyTranscripts as $xscript) {
@@ -57,6 +59,29 @@ class HeraldTranscript extends HeraldDAO {
     return implode(', ', $ids);
   }
 
+  public static function saveXHeraldRulesHeader($phid, $header) {
+    queryfx(
+      id(new HeraldTranscript())->establishConnection('w'),
+      'INSERT INTO %T (phid, header) VALUES (%s, %s)
+        ON DUPLICATE KEY UPDATE header = VALUES(header)',
+      self::TABLE_SAVED_HEADER,
+      $phid,
+      $header);
+  }
+
+  public static function loadXHeraldRulesHeader($phid) {
+    $header = queryfx_one(
+      id(new HeraldTranscript())->establishConnection('r'),
+      'SELECT * FROM %T WHERE phid = %s',
+      self::TABLE_SAVED_HEADER,
+      $phid);
+    if ($header) {
+      return idx($header, 'header');
+    }
+    return null;
+  }
+
+
   protected function getConfiguration() {
     // Ugh. Too much of a mess to deal with.
     return array(

src/applications/herald/storage/transcript/base/__init__.php

@@ -8,6 +8,7 @@
 
 phutil_require_module('phabricator', 'applications/herald/storage/base');
 phutil_require_module('phabricator', 'applications/phid/storage/phid');
+phutil_require_module('phabricator', 'storage/queryfx');
 
 phutil_require_module('phutil', 'utils');