Skip sorting in ArrayTagSet for SortedMaps

[kilink]

When tags are supplied in a SortedMap, skip the sorting step. Additionally, skip deduping when tags are supplied in a Map in general.

[brharrington]

Should this also check if the natural ordering is explicit?

private boolean hasNaturalOrder(SortedMap<String, String> ts) {
  return ts.comparator() == null || ts.comparator() == Comparator.<String>naturalOrder();
}

That would cover usage like new TreeMap<>(Comparator.naturalOrder()), though not new TreeMap<>(String::compareTo).

[kilink]

I thought about checking for Comparator.naturalOrder(), although I think it might be unusual to explicitly supply that comparator since the Javadoc for SortedMap / TreeMap indicate natural ordering is the default. I can go ahead and add a check for that anyway, but I think it's not possible to cover all scenarios (Guava collections use an explicit comparator for natural ordering that is different than Comparator.naturalOrder(), and String::compareTo like you mentioned.

[kilink]

Okay, I've updated the PR to check for Comparator.naturalOrder() as well.