Merge branch 'stable-7.1'

* stable-7.1:
  Add missing @since 7.1 to UploadPack#implies
  ResolveMerger: Allow setting the TreeWalk AttributesNodeProvider
  Add Union merge strategy support

Change-Id: Ib1c1725578e522c88f80f050d221a517bf012017

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
Simple merge