Polish devtools declaration documentation

spring-boot-docs/src/main/asciidoc/index.adoc

@@ -40,6 +40,7 @@ Phillip Webb; Dave Syer; Josh Long; Stéphane Nicoll; Rob Winch; Andy Wilkinson;
 :spring-data-mongo-javadoc: http://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb
 :spring-data-rest-javadoc: http://docs.spring.io/spring-data/rest/docs/current/api/org/springframework/data/rest
 :gradle-userguide: http://www.gradle.org/docs/current/userguide
+:propdeps-plugin: https://github.com/spring-projects/gradle-plugins/tree/master/propdeps-plugin
 :ant-manual: http://ant.apache.org/manual
 // ======================================================================================
 

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -819,6 +819,7 @@ devtools support, simply add the module dependency to your build:
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-devtools</artifactId>
+			<optional>true</optional>
 		</dependency>
 	</dependencies>
 ----
@@ -831,10 +832,13 @@ devtools support, simply add the module dependency to your build:
 	}
 ----
 
-
 NOTE: Developer tools are automatically disabled when running a fully packaged
 application. If your application is launched using `java -jar` or if it's started using a
-special classloader, then it is considered a "`production application`".
+special classloader, then it is considered a "`production application`". Flagging the
+dependency as optional is a best practice that prevents devtools from being transitively
+applied to other modules using your project. Gradle does not support `optional`
+dependencies out-of-the-box so you may want to have a look to the
+{propdeps-plugin}[`propdeps-plugin`] in the meantime.