Merge branch 'stable-3.1' into stable-3.2

* stable-3.1:
  Set version to 2.16.29-SNAPSHOT
  Set version to 2.16.28
  Use JGit 5.1.15.202012011955-r javadoc to resume release build

Change-Id: I6365a2a23ff8d64d81fbef64d3d72aafcb06580e