fix compare_paths_lt irreflexivity for equal paths

[T90REAL]

Solve #628.
Fix compare_paths_lt to align with Python’s strict ordering contract.

[funkyfuture]

please provide tests that have a practical impact where you prove that the current implementation isn't sufficient.

if you propose such a significant change, also add tests that cover the possible edge cases between the current state and your proposal, so we can be sure that the current sorting behaviour persists.

then (again), i don't know where you take that strong contract from and why you think it would be mandatory in that case.

[T90REAL]

Thanks for your response. My original thought is that if err < err == True would cause some function does not work as designed, for example the bisect_left function. After reconsidering the context, I agree it doesn’t have a significant impact on the behavior. I’ll close the PR here, sorry for the noise.

[funkyfuture]

well, let's consider this an academic exercise.