It seems weird to have two ways of comparing versions.
Good point, I'll remove the compareTo and just use the existing onOrAfter.
Is there somewhere we could have a more direct test than deletion policy tests?
I'll try to make a more direct test (TestSegmentInfos)...
We dont technically need to change file formats to implement this, it could be computed from the segments on read in the 4.0-5.2 case?
That's what I do in the patch ... if SIS was written by >= 5.3, I pull the min version that we wrote into the header (and throw IndexTooOldExc if it's too old), else I re-compute it on load.