superflore-gen-oe-recipes: Don't create a commit when ROS_DISTRO-cache.yaml hasn't changed

superflore-gen-oe-recipes should not create a commit when there are no changes to <ROS_DISTRO>-cache.yaml, eg, running it twice in a row. Instead, one is created, and more surprisingly, it has one of the following commit messages even though no new recipes appear in the commit:

        # Crystal Changes:
        * ament_cmake_include_directories 0.6.1
        * fmi_adapter_examples 0.1.4-1
        * gazebo_ros_pkgs 3.2.0
        * launch_ros 0.7.4
        * qt_gui_cpp 1.0.6-1
        * rcl_action 0.6.6-1
        * rosbag2_storage_default_plugins 0.0.7
        * rosbag2_transport 0.0.7
        * rosidl_typesupport_connext_cpp 0.6.4
        * rosidl_typesupport_cpp 0.6.3
        * rosidl_typesupport_fastrtps_cpp 0.6.1
        * rqt_gui_cpp 1.0.2
        * rqt_gui_py 1.0.2
        * rviz_rendering_tests 5.1.0
        * system_modes_examples 0.1.3-1

        # Dashing Changes:
        * ament_cmake_export_interfaces 0.7.3-1
        * demo_nodes_cpp_native 0.7.8-1
        * fmi_adapter_examples 0.1.5-1
        * gazebo_ros_pkgs 3.3.3-1
        * launch_testing_ament_cmake 0.8.5-3
        * qt_gui_cpp 1.0.6-1
        * rclcpp_components 0.7.7-1
        * rmw_implementation_cmake 0.7.2-1
        * rosbag2_tests 0.1.4-1
        * rosidl_generator_cpp 0.7.5-1
        * rosidl_typesupport_cpp 0.7.1-1
        * rosidl_typesupport_fastrtps_cpp 0.7.1-1
        * rosidl_typesupport_introspection_cpp 0.7.5-1
        * rqt_gui_cpp 1.0.4-1
        * rqt_py_common 1.0.4-1
        * rviz_rendering_tests 6.1.3-1
        * sros2_cmake 0.7.1-1
        * tf2_ros 0.11.4-1

        # Melodic Changes:
        * arbotix_sensors 0.10.0
        * bondpy 1.8.3
        * calibration_launch 0.10.14
        * cartographer_ros_msgs 1.0.0-1
        * cob_android_msgs 0.1.6-1
        * cob_control_mode_adapter 0.8.0-1
        * cob_navigation_global 0.6.8-1
        * controller_manager_tests 0.15.1
        * dataspeed_can_tools 1.0.12
        * dataspeed_pds_can 1.0.2
        * dataspeed_ulc_can 0.0.4-1
        * dbw_mkz_twist_controller 1.2.3-1
        * desktop_full 1.4.1
        * distance_map_core 0.1.0-1
        * dynamixel_workbench_single_manager_gui 2.0.0
        * ecl_core_apps 0.62.2
        * exotica_collision_scene_fcl_latest 5.0.0
        * exotica_core_task_maps 5.0.0
        * exotica_time_indexed_rrt_connect_solver 5.0.0
        * gazebo_ros_control 2.8.4
        * grid_map_pcl 1.6.1
        * igvc_self_drive_gazebo_plugins 0.1.4-1
        * imagezero_ros 0.2.4
        * joystick_drivers 1.13.0-1
        * jsk_interactive_marker 2.1.5
        * jsk_pcl_ros_utils 1.2.10
        * jsk_recognition_utils 1.2.10
        * julius_ros 2.1.13-1
        * mapviz_plugins 1.1.1-1
        * mavros_msgs 0.32.1-1
        * mongodb_store_msgs 0.5.1-2
        * moveit_planners_chomp 1.0.2-1
        * moveit_planners_ompl 1.0.2-1
        * moveit_ros_planning_interface 1.0.2-1
        * multisense_description 4.0.2
        * nav2d_localizer 0.4.2
        * neonavigation_common 0.4.2-1
        * nodelet_topic_tools 1.9.16
        * open_manipulator_teleop 2.0.1
        * open_manipulator_with_tb3_waffle_pi_moveit 1.1.0-2
        * people_tracking_filter 1.2.0-1
        * pr2_mechanism_diagnostics 1.8.18
        * qt_gui_core 0.3.11
        * ridgeback_gazebo_plugins 0.1.0-1
        * robot_activity_msgs 0.1.1
        * robot_calibration_msgs 0.6.0
        * robot_controllers_interface 0.6.0
        * ros1_ign_point_cloud 0.7.0-1
        * rosbag_storage 1.14.3
        * rosmon_msgs 2.1.1-1
        * rosserial_arduino 0.8.0
        * rotors_gazebo_plugins 2.2.3
        * rqt_bag_plugins 0.4.12
        * rqt_gui_py 0.5.0
        * rqt_py_common 0.5.0
        * rslidar_driver 1.0.2
        * smach_ros 2.0.1
        * teleop_tools_msgs 0.3.0
        * tf2_kdl 0.6.5
        * turtle_tf2 0.2.2
        * turtlebot3_automatic_parking_vision 1.1.0
        * turtlebot3_autorace_control 1.2.0
        * turtlebot3_slam 1.2.2-1
        * unique_identifier 1.0.6
        * uuv_gazebo_plugins 0.6.13
        * uuv_sensor_ros_plugins_msgs 0.6.13
        * uuv_world_ros_plugins_msgs 0.6.13
        * variant_msgs 0.1.5
        * wave_gazebo_plugins 1.2.0-1
        * webrtc_ros 59.0.3
        * wge100_camera_firmware 1.8.2-1
        * xpp_msgs 1.0.10

ros-infrastructure / superflore

superflore-gen-oe-recipes: Don't create a commit when ROS_DISTRO-cache.yaml hasn't changed #227