Deprecate $wgUseESI

This was an experimental Squid 3 feature which is now defunct.

Change-Id: I799d87309b0dc77100900b75040fa9b85a35fc9a

RELEASE-NOTES-1.33

@@ -56,6 +56,8 @@ because of Phabricator reports.
 * …
 
 === Deprecations in 1.33 ===
+* The configuration option $wgUseESI has been deprecated, and is expected
+  to be removed in a future release.
 * …
 
 === Other changes in 1.33 ===

includes/AjaxResponse.php

@@ -186,6 +186,7 @@ class AjaxResponse {
 				# Surrogate-Control controls our CDN, Cache-Control downstream caches
 
 				if ( $this->mConfig->get( 'UseESI' ) ) {
+					wfDeprecated( '$wgUseESI = true', '1.33' );
 					header( 'Surrogate-Control: max-age=' . $this->mCacheDuration . ', content="ESI/1.0"' );
 					header( 'Cache-Control: s-maxage=0, must-revalidate, max-age=0' );
 				} else {

includes/DefaultSettings.php

@@ -2736,6 +2736,7 @@ $wgUseSquid = false;
 
 /**
  * If you run Squid3 with ESI support, enable this (default:false):
+ * @deprecated in 1.33. This was a now-defunct experimental feature.
  */
 $wgUseESI = false;
 

includes/OutputPage.php

@@ -2460,6 +2460,7 @@ class OutputPage extends ContextSource {
 				!$this->haveCacheVaryCookies()
 			) {
 				if ( $config->get( 'UseESI' ) ) {
+					wfDeprecated( '$wgUseESI = true', '1.33' );
 					# We'll purge the proxy cache explicitly, but require end user agents
 					# to revalidate against the proxy on each visit.
 					# Surrogate-Control controls our CDN, Cache-Control downstream caches