Clarify MainClass option of the bootRepackage task

Closes gh-2477

spring-boot-docs/src/main/asciidoc/appendix-executable-jar-format.adoc

@@ -230,6 +230,10 @@ Manifest entry keys are formed by capitalizing initial letters of words and chan
 separator to "`-`" from "`.`" (e.g. `Loader-Path`). The exception is `loader.main` which
 is looked up as `Start-Class` in the manifest for compatibility with `JarLauncher`).
 
+TIP: Build plugins automatically move the `Main-Class` attribute to `Start-Class` when
+the fat jar is built. If you are using that, specify the name of the class to launch using
+the `Main-Class` attribute and leave out `Start-Class`.
+
 Environment variables can be capitalized with underscore separators instead of periods.
 
 * `loader.home` is the directory location of an additional properties file (overriding

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -246,7 +246,8 @@ its {dependency-management-plugin-documentation}[documentation].
 [[build-tool-plugins-gradle-packaging]]
 === Packaging executable jar and war files
 Once the `spring-boot` plugin has been applied to your project it will automatically
-attempt to rewrite archives to make them executable using the `bootRepackage` task. You
+attempt to rewrite archives to make them executable using the
+<<build-tool-plugins-gradle-repackage-configuration,`bootRepackage` task>>. You
 should configure your project to build a jar or war (as appropriate) in the usual way.
 
 The main class that you want to launch can either be specified using a configuration
@@ -254,6 +255,9 @@ option, or by adding a `Main-Class` attribute to the manifest. If you don't spec
 main class the plugin will search for a class with a
 `public static void main(String[] args)` method.
 
+TIP: Check <<build-tool-plugins-gradle-repackage-configuration>> for a full list of
+configuration options.
+
 To build and run a project artifact, you can type the following:
 
 [indent=0]