* stable-2.16:
CommentJsonMigrator: Improve error handling if comment note is too large
ChangeApi: Add default implementation of setPrivate with null message
ChangeApi: Annotate nullable message parameters as @Nullable
ProjectApi: Add methods to get/set project's HEAD
CommitApi: Add method to get "included in" information
Upgrade elasticsearch-rest-client to 6.5.4
Add the GWT hash separator to the GWT url
Change-Id: I206f68848adf7fad2a0dc3d8b12db28c9e8bf7e5
3a02ff24e6