Syncronized callbacks in ROS2

@allenh1 Thank you for you kindly reminders.
I’m afraid I didn’t put my question clear.
Let me take message_filters as an example, if I want to port message_filters to ROS2, which branch I should forked from the ros_comm project. lunar_devel or kinetic_devel or some else, as there are too much branch.

Regards,
Peter Han