Release tags do not live on master: 3.15.2 through 3.15.6 were tagged on branch
3.15, so git describe reaches only 3.15.1 and dev builds were stamped
3.15.2.dev<n>. Besides being confusing, rpm and dpkg both rank the released
3.15.6 above that, so a dev package will not install over a released one.
Add a top-level VERSION file naming the release the branch is working toward
(4.0.0 on master) and a mkversion helper that stamps packages from it, keeping
the tag-derived value as a floor so a forgotten bump cannot go backwards.
mkversion also replaces the block copy-pasted into seven build scripts, and
makesetup no longer writes a per-package VERSION file, so the stale checked-in
confluent_common/VERSION goes with it.
Markus Hilger
Jarrod Johnson