Add a hook_farm_update_exclude_config() to allow modules to exclude config from automatic updates.

modules/core/update/farm_update.api.php

@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * @file
+ * Hooks provided by farm_update.
+ *
+ * This file contains no working PHP code; it exists to provide additional
+ * documentation for doxygen as well as to document hooks in the standard
+ * Drupal manner.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Specify config items that should be excluded from automatic updates.
+ *
+ * @return array
+ *   An array of config item names.
+ */
+function hook_farm_update_exclude_config() {
+  return [
+    'core.extension',
+    'system.date',
+  ];
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */

modules/core/update/farm_update.services.yml

@@ -1,4 +1,4 @@
 services:
   farm.update:
     class: Drupal\farm_update\FarmUpdate
-    arguments: [ '@entity_type.manager', '@config_update.config_diff', '@config_update.config_list', '@config_update.config_update' ]
+    arguments: [ '@module_handler', '@entity_type.manager', '@config_update.config_diff', '@config_update.config_list', '@config_update.config_update' ]

modules/core/update/src/FarmUpdate.php

@@ -6,12 +6,20 @@ use Drupal\config_update\ConfigDiffer;
 use Drupal\config_update\ConfigListerWithProviders;
 use Drupal\config_update\ConfigReverter;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
 
 /**
  * Farm update service.
  */
 class FarmUpdate implements FarmUpdateInterface {
 
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
   /**
    * The entity manager.
    *
@@ -43,6 +51,8 @@ class FarmUpdate implements FarmUpdateInterface {
   /**
    * Constructs a FarmUpdate object.
    *
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
    * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_manager
    *   The entity type manager.
    * @param \Drupal\config_update\ConfigDiffer $config_diff
@@ -52,7 +62,8 @@ class FarmUpdate implements FarmUpdateInterface {
    * @param \Drupal\config_update\ConfigReverter $config_update
    *   The config reverter.
    */
-  public function __construct(EntityTypeManagerInterface $entity_manager, ConfigDiffer $config_diff, ConfigListerWithProviders $config_list, ConfigReverter $config_update) {
+  public function __construct(ModuleHandlerInterface $module_handler, EntityTypeManagerInterface $entity_manager, ConfigDiffer $config_diff, ConfigListerWithProviders $config_list, ConfigReverter $config_update) {
+    $this->moduleHandler = $module_handler;
     $this->entityManager = $entity_manager;
     $this->configDiff = $config_diff;
     $this->configList = $config_list;
@@ -64,8 +75,11 @@ class FarmUpdate implements FarmUpdateInterface {
    */
   public function rebuild(): void {
 
-    // Build a list of config to revert.
-    $revert_config = $this->getDifferentItems('type', 'system.all');
+    // Get a list of excluded config.
+    $exclude_config = $this->getExcludedItems();
+
+    // Build a list of config to revert, without excluded config.
+    $revert_config = array_diff($this->getDifferentItems('type', 'system.all'), $exclude_config);
 
     // Iterate through config items and revert them.
     foreach ($revert_config as $name) {
@@ -91,6 +105,22 @@ class FarmUpdate implements FarmUpdateInterface {
     }
   }
 
+  /**
+   * Lists excluded config items.
+   *
+   * Lists config items that should be excluded from all automatic updates.
+   *
+   * @return array
+   *   An array of config item names.
+   */
+  protected function getExcludedItems() {
+
+    // Ask modules for config exclusions.
+    $exclude_config = $this->moduleHandler->invokeAll('farm_update_exclude_config');
+
+    return $exclude_config;
+  }
+
   /**
    * Lists differing config items.
    *