Github user sihuazhou commented on the issue:
https://github.com/apache/flink/pull/5578
@StefanRRichter I have addressed your suggestions, except the one that to
make the `if` a bit complex, instead I introduced a `Predicate` for the
`pruneCheckpoints()`. I not sure whether it is ok to you, if you still against
doing so, I'd like to change the code as to make the `if` a bit complex.---
