update all is_reserved templates each time

CRM/Upgrade/Form.php

@@ -912,6 +912,10 @@ public function setPreUpgradeMessage(&$preUpgradeMessage, $currentVer, $latestVe
         }
       }
     }
+    // Now make sure *all* reserved ones got updated. Might be inefficient, but there's only about 30.
+    // Note this has to come after the template update above, otherwise that can't tell which ones the site
+    // has changed.
+    CRM_Upgrade_Incremental_MessageTemplates::updateReservedTemplates($latestVer);
   }
 
 }

CRM/Upgrade/Incremental/MessageTemplates.php

@@ -487,6 +487,31 @@ public function getUpgradeMessages() {
     return $messages;
   }
 
+  /**
+   * Update reserved message templates.
+   * @param string $version
+   */
+  public static function updateReservedTemplates($version) {
+    if (version_compare($version, '5.26', '<')) {
+      // We can't do this before workflow_name was introduced. Strictly speaking we don't care until 5.54.
+      return;
+    }
+    $dao = CRM_Core_DAO::executeQuery("SELECT id, workflow_name FROM civicrm_msg_template WHERE is_reserved=1");
+    while ($dao->fetch()) {
+      foreach (['html', 'text', 'subject'] as $type) {
+        $content = file_get_contents(\Civi::paths()->getPath('[civicrm.root]/xml/templates/message_templates/' . $dao->workflow_name . '_' . $type . '.tpl'));
+        if ($content) {
+          CRM_Core_DAO::executeQuery(
+            "UPDATE civicrm_msg_template SET msg_{$type} = %1 WHERE id = %2", [
+              1 => [$content, 'String'],
+              2 => [$dao->id, 'Integer'],
+            ]
+          );
+        }
+      }
+    }
+  }
+
   /**
    * Update message templates.
    */