[boost] RE process (prospective from a retired FreeBSD committer)...

Subject: [boost] RE process (prospective from a retired FreeBSD committer)...
From: Sean Chittenden (sean_at_[hidden])
Date: 2011-01-27 13:58:11

I originally sent this to Eric but am cleaning it up and reposting here per his suggestion.

From an outsider's perspective it appears as though the lack of branching/merging tied to release management is the biggest issue for Boost at present.

I'm a retired FreeBSD committer, I wanted to point out how the FreeBSD community deals with release engineering and see if there are a few nugget policies that could be cherry picked for boost.  FreeBSD's process has been in place and refined for the last 15 years and comes with already written documentation as a starting point.  It's not perfect, but there's a pound of prevention that comes via policy that no tool can replicate.

head/trunk/tip is known as the -CURRENT branch.  Released versions for production used (or are in prep for being released) are known as -STABLE branches.  When FreeBSD 8 was being developed, people committed to HEAD (aka -CURRENT).  When the re@ team called for a freeze for release and -CURRENT was in sufficiently good condition, they branched HEAD in to RELENG_8_STABLE.  Everything in RELENG_8_* is expected to be production quality (or nearing it).  Upon release of 8.0, RELENG_8 was branched again to RELEASE_8_0.  8.1, 8.2, etc were all created from RELENG_8_STABLE.  Fixes for things in stable go to -CURRENT first, then are back patched to the appropriate stable releases, colloquially known as MFC's or Merge From -CURRENT.

-CURRENT is the wild west of OS development and repo trash.  Use at your own risk.  Stability and likelihood of all tests passing is marginal, at best.  Towards the end of a given major version -CURRENT becomes more stable, but once -STABLE has been branched it quickly degenerates some as people implement the impetus to checkin new features.

-STABLE should always be passing 100% of the regression tests present in the branch at all times.

A quick doc on merging between branches:  http://wiki.freebsd.org/SVN_Merging

I don't know how wide spread it is and despite svk having gone in to maintenance mode, use of svk has merit (partial checkouts):

http://svk.bestpractical.com/view/HomePage

http://www.freebsd.org/releng/

Anyway, the way that FreeBSD handles its permissions and merging from one branch to the next is via the commit message and commit hooks and approvals from different people wearing different hats.  A few examples:

http://lists.freebsd.org/pipermail/svn-src-stable/2011-January/008657.html

has an MFC line in there to denote the changes included.  The commit handler verifies that the diffed files largely match (at least it used to back in the day when I was committing via CVS).

http://lists.freebsd.org/pipermail/svn-src-stable/2011-January/008683.html

Reviewed by commit header.  This gives greater latitude in terms of what can be included in the commit.

http://lists.freebsd.org/pipermail/svn-src-stable/2011-January/008808.html

And the 'Approved by' commit header.  Once a release is frozen, all commits need to have this tag.  The commit will fail without it and if someone commit with that line and didn't have permission to do so, as a policy, the commit is always reverted 100% of the time as a matter of principle.  Frequently it's re-committed, but it's a big slap to the back of the hands to have to go through the process again.  Needless to say, the commit mailing list is the most active and widely read list as a result.  And tons of code gets reviewed with many eyes viewing it as a result.

There are other bits worth noting, acls apply to different parts of the tree (doc-re vs src-re), but I don't know how many people actually follow boost's commit log on a per commit basis, but given 100% of all commits go to a single mailing list, it seems like the current list infrastructure makes that kind of review process unsustainable for Joe Reviewer (vs. the shorter abridged commit messages w/ a link to the actual diff).

Lots of people fork FreeBSD to do experimental work out of the tree via git and hg, but the monolithic and serialized commit/review process seems to be working quite well from my perspective.  A little bureaucratic but very stable and democratic without reliance on any one person to push the release forward.  Anyway, food for thought. Hopefully there's something there that you can pick out of value.

If you have questions, feel free to ask.  -sc

--
Sean Chittenden
sean_at_[hidden]