Document the use of --args to pass arguments to bootRun

Closes gh-1176

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/asciidoc/index.adoc

@@ -11,6 +11,7 @@ Andy Wilkinson
 :dependency-management-plugin-documentation: {dependency-management-plugin}/blob/master/README.md
 :gradle-userguide: https://docs.gradle.org/current/userguide
 :gradle-dsl: https://docs.gradle.org/current/dsl
+:gradle-api: https://docs.gradle.org/current/javadoc
 :application-plugin: {gradle-userguide}/application_plugin.html
 :groovy-plugin: {gradle-userguide}/groovy_plugin.html
 :java-plugin: {gradle-userguide}/java_plugin.html

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/asciidoc/running.adoc

@@ -42,6 +42,22 @@ include::../gradle/running/application-plugin-main-class-name.gradle[tags=main-c
 
 
 
+[[running-your-application-passing-arguments]]
+=== Passing arguments to your application
+Like all `JavaExec` tasks, arguments can be passed into `bootRun` from the command line
+using `--args='<arguments'>` when using Gradle 4.9 or later. For example, to run your
+application with a profile named `dev` active the following command can be used:
+
+[source,bash,indent=0,subs="verbatim"]
+----
+	$ ./gradlew bootRun --args='--spring.profiles.active=dev'
+----
+
+See {gradle-api}/org/gradle/api/tasks/JavaExec.html#setArgsString-java.lang.String-[the
+javadoc for `JavaExec.setArgsString`] for further details.
+
+
+
 [[running-your-application-reloading-resources]]
 === Reloading resources
 If devtools has been added to your project it will automatically monitor your