Clarify plugin documentation for requiresUnpack

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/RepackageMojo.java

@@ -121,7 +121,9 @@ public class RepackageMojo extends AbstractDependencyFilterMojo {
 	private LayoutType layout;
 
 	/**
-	 * A list of the libraries that must be unpacked from fat jars in order to run.
+	 * A list of the libraries that must be unpacked from fat jars in order to run. Specify
+	 * each library as a <code>&lt;dependency&gt;</code> with a <code>&lt;groupId&gt;</code> and a
+	 * <code>&lt;artifactId&gt;</code> and they will be unpacked at runtime in <code>$TMPDIR/spring-boot-libs</code>.
 	 * @since 1.1
 	 */
 	@Parameter