Could you push the 'rawhide' branch in your fork as well to see if that makes a difference?

no difference

Note tat the PR adds a merge commit with a branch of unrelated history. That may be the problem.

Note tat the PR adds a merge commit with a branch of unrelated history. That may be the problem.

Could be, what surprises me more is that it still finds a list of commits
differing but doesn't show a diff.

Merged manually. As a reproducer, use https://src.fedoraproject.org/fork/churchyard/rpms/python2.7/diff/f33..py2_macros instead.

Thanks for the reproducer