Merge pull request #28495 from Artur-

* pr/28495:
  Polish "Log the reason that led Devtools to restart the app"
  Log the reason that led Devtools to restart the app

Closes gh-28495

Author: snicoll

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,9 @@
 import java.net.URL;
 import java.util.List;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -94,6 +97,8 @@ LiveReloadServerEventListener liveReloadServerEventListener(OptionalLiveReloadSe
 	@ConditionalOnProperty(prefix = "spring.devtools.restart", name = "enabled", matchIfMissing = true)
 	static class RestartConfiguration {
 
+		private static final Log restarterLogger = LogFactory.getLog(Restarter.class);
+
 		private final DevToolsProperties properties;
 
 		RestartConfiguration(DevToolsProperties properties) {
@@ -105,6 +110,10 @@ ApplicationListener<ClassPathChangedEvent> restartingClassPathChangedEventListen
 				FileSystemWatcherFactory fileSystemWatcherFactory) {
 			return (event) -> {
 				if (event.isRestartRequired()) {
+					if (restarterLogger.isDebugEnabled()) {
+						restarterLogger.debug(
+								"Application restart required due to the following changes: " + event.getChangeSet());
+					}
 					Restarter.getInstance().restart(new FileWatchingFailureHandler(fileSystemWatcherFactory));
 				}
 			};