Issue #2960605 by anmolgoyal74, surbz, msankhala, arunkumark, jibran, alexpott: Add docs to the empty hook_update_N used for cache clearing

core/modules/image/image.install

@@ -67,4 +67,8 @@ function image_requirements($phase) {
  */
 function image_update_8201() {
   // Empty update to trigger a cache flush.
+
+  // Use hook_post_update_NAME() instead to clear the cache. The use of
+  // hook_update_N() to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }

core/modules/system/system.install

@@ -1837,6 +1837,10 @@ function system_update_8200(&$sandbox) {
  */
 function system_update_8201() {
   // Empty update to cause a cache rebuild.
+
+  // Use hook_post_update_NAME() instead to clear the cache.
+  // The use of hook_update_N() to clear the cache has been deprecated
+  // see https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -1844,6 +1848,10 @@ function system_update_8201() {
  */
 function system_update_8202() {
   // Empty update to cause a cache rebuild.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**

core/modules/update/update.install

@@ -158,4 +158,8 @@ function _update_requirement_check($project, $type) {
 function update_update_8001() {
   // Empty update forces a call to drupal_flush_all_caches() which rebuilds the
   // router.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }

core/modules/views/views.install

@@ -315,6 +315,10 @@ function views_update_8003() {
   // Empty update to cause a cache flush so that views data is rebuilt. Entity
   // types that don't implement a list builder cannot have the entity operations
   // field.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -322,6 +326,10 @@ function views_update_8003() {
  */
 function views_update_8004() {
   // Empty update to cause a cache flush so that views data is rebuilt.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -329,6 +337,10 @@ function views_update_8004() {
  */
 function views_update_8005() {
   // Empty update function to rebuild the views data.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -336,6 +348,10 @@ function views_update_8005() {
  */
 function views_update_8100() {
   // Empty update to cause a cache flush so that views data is rebuilt.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -365,6 +381,10 @@ function views_update_8101() {
  */
 function views_update_8200() {
   // Empty update to cause a cache rebuild so that the container is rebuilt.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**
@@ -372,6 +392,10 @@ function views_update_8200() {
  */
 function views_update_8201() {
   // Empty update to cause a cache rebuild so that config schema get refreshed.
+
+  // Use hook_post_update_NAME() instead to clear the cache.The use
+  // of hook_update_N to clear the cache has been deprecated see
+  // https://www.drupal.org/node/2960601 for more details.
 }
 
 /**