We get problems like this: nodejs/node@75318e4#commitcomment-24788304 all the time. The solution we have is to put the PR-URL (or other relevant metadata) in a comment on the commit.
If branch-diff
could check this it would alleviate the problem for LTS maintainers.
I was going to have a look at implementing this but never got around to it. Thought I'd put this here in case anyone else has the time and inclination.
cc/ @MylesBorins @rvagg