The build session state is managed by the `BuildSessionState` class.
An instance is created at the start of a Gradle invocation and discarded at the end of that invocation.

The build session state also includes "cross session" state that is shared with any "nested" sessions that need to be created.

        promote.assertTasks("prepReleaseNightly promoteReleaseNightly")
        assertEquals(expectedGradleParams, promote.gradleParams)
    }

    @Test
    fun `start release cycle promotion build type runs one gradle invocation`() {
        val model = setupModelFor("master")
        val startReleaseCycle = model.findBuildTypeByName("Start Release Cycle")

        val steps = startReleaseCycle.steps.items
        assertEquals(1, steps.size)