Currently I am using the GradleLauncher to repeat a task from within a task.

Example of how I use it now:

// The option defaults were made nice for individual users of the build system. For the installers we
// need to set them specifically for our needs. Here we turn on all the time consuming tasks that
// most people don't want to have to suffer through.
def startArgs = ['someTask','someArg','someArg','someArg'] as String[]

//We need to make a default launcher factory to build our launcher for us, it also handles creating our start parameter.
GradleLauncherFactory gradleLauncherFactory = new DefaultGradleLauncherFactory()
StartParameter startParameterArgs = gradleLauncherFactory.createStartParameter(startArgs)
def buildFile = new File(rootDir, '/buildSrc/root.gradle')
startParameterArgs.setBuildFile(buildFile)

//Once the start parameter is created we can use the launcher factory to create our launcher and run it.
GradleLauncher gradleLauncher = gradleLauncherFactory.newInstance(startParameterArgs)
BuildResult buildResult
buildResult = gradleLauncher.run()
buildResult.rethrowFailure()//If it fails for any reason this will throw a failure for the current process and let us know why.

I would prefer it to be simpler to call on another task from within a currently operating task, something like this would be preferable:

def startArgs = ['someTask','someArg','someArg','someArg'] as String[]
GradleTask someTask = new GradleTask(startArgs)
someTask.run()