Discussed with @jseldess: it would be useful when producing release notes for a branch to mark which changes are also duplicated on other release branches (or master).

For example when looking at 2.0.x changes mark a RN as "back-ported from ..."
Or when looking at 2.1-alpha changes mark a RN as "also back-ported to ..."

Preferably the annotation should be simple and easy to parse, so that a script can further automatically recognize/process it.