Our new policy is to use the "rebase" method and slice all the Neon
commits into a nice patch set when doing a new major version, and use
"merge" method on minor version upgrades on the release branches.
"git merge" preserves the git history of Neon commits on the Postgres
branches. While it's nice to rebase all the Neon changes to a logical
patch set against upstream, having to do it between every minor release
is a fair amount work, and it loses the history, and is more
error-prone.
