Add ExitStatus to Command.run()

The main difference for now is the removal of the --nohup
(slightly hacky) option in TestCommand. Now a TestCommand
can signal to its caller that it wants to be hung up.

Fixes gh-975

spring-boot-cli/src/test/java/cli/command/CustomCommand.java

@@ -28,8 +28,9 @@ public class CustomCommand extends AbstractCommand {
 	}
 
 	@Override
-	public void run(String... args) throws Exception {
+	public ExitStatus run(String... args) throws Exception {
 		System.err.println("Custom Command Hello");
+		return ExitStatus.OK;
 	}
 
 }

spring-boot-cli/src/test/java/org/springframework/boot/cli/CliTester.java

@@ -75,10 +75,7 @@ public class CliTester implements TestRule {
 	}
 
 	public String test(String... args) throws Exception {
-		String[] argsToUse = new String[args.length + 1];
-		System.arraycopy(args, 0, argsToUse, 1, args.length);
-		argsToUse[0] = "--nohup";
-		Future<TestCommand> future = submitCommand(new TestCommand(), argsToUse);
+		Future<TestCommand> future = submitCommand(new TestCommand(), args);
 		this.commands.add(future.get(this.timeout, TimeUnit.MILLISECONDS));
 		return getOutput();
 	}