[Mailman-Developers] Should we move to Bazaar?

[Stephen J. Turnbull]

Barry Warsaw writes:

 > think this is a good time to ask whether we should move from  
 > Subversion to Bazaar <http://www.bazaar-vcs.org> for our source code  
 > revision control system.

I would rank Bazaar(-ng == bzr) third behind git and Mercurial.  I
like git because it tastes like Mom's home cooking.  Er, I mean, the
git model has a strong flavor of Lisp, although "cons", "car", "cdr",
and "get" are about the only operations fully implemented yet.  This
has long been the way I think about vcses, despite long flirtations
with GNU Arch and Darcs.  While Linus is not primarily interested in
vcses, the fact that he chose to implement his personal vcs as a
dialect of the oldest (and still going strong) computer language is
indicative of future possibilities.  If there's going to be another
quantum leap in vcses in the next few years, my bet is that the
prototype will be a child of git.

Mercurial is second because it is likely to be the choice of my main
project, XEmacs.  It has strong recommendations from people working at
Sun, where it is already becoming widespread.  Documentation is better
than git's, and much better for the new user.  It's developed by vcs
pros.

Bazaar is close to Mercurial, for similar reasons (s/Sun/Canonical/).
However, I give Mercurial the edge because it is being developed by
people who develop vcses for their own sake, while Canonical has
demonstrated that their interest in vcses is instrumental to their
development business.  Nothing wrong with that per se, but I think
that dvcses have a long way to go to reach maturity (viz Darcs's
"theory of patches" approach and its innovative and addictive UI not
yet copied by any of the other main contenders).  I think it's worth
going with Mercurial for the possibility of picking up on the "next
next" generation early.  While the whole point of bzr is to be to tla
as svn is to cvs. :-)

I should remark that bzr's diffs are currently the best in the
business.  See my reply to Edward Elhauge and also Bram Cohen's blog
http://bramcohen.livejournal.com/37690.html.  This advantage probably
won't last long, though---git and Mercurial both have their diff
commands well-modularized, it won't be hard to add.

Re some vcses that IMO won't fly:

Darcs, although very interesting as a radical departure from the other
dvcses, is IMO not ready for prime time yet.  Development is somewhat
slowed by being written in Haskell, which makes it hard for most users
to contribute directly.  It also has some really dire performance
problems that show up in ordinary usage for a non-negligible fraction
of projects.

The Arch 1 family (arx, tla, baz) is a non-starter.  It's very usable,
but for future development, it's orphaned.  The main author, Tom Lord,
is once again being a radical innovator, movint on to Arch 2.  But
Arch 2 (also known as "revc") is not ready for "real work" yet, it may
not even be self-hosting at this point.  In any case, Tom is not
currently able to push development very actively.

There are a couple of others out there, but I think the main
contenders are Bazaar, git, and Mercurial.  IMO any of them will do.

 > Bazaar is a distributed version control system.  This is really the  
 > crucial different between centralized systems such as Subversion and  
 > CVS, and it's the main draw for wanting to switch.

It also means that at the present time there's very little difference
between git, Mercurial, and Bazaar in use.  The real difference is in
the goals of the maintainers, namely "keeping Linus happy", "making
the best possible dvcs", and "what we use at work."  All of these have
their advantages.

Everything that Barry wrote that I've cut out I agree with, strongly.

 > One more thing.  If we move to Bazaar, I would host the branches on  
 > Launchpad.net, which -- full disclosure again -- is developed,  
 > managed, and paid for by my employer.  Why Launchpad?  Because it's  
 > convenient, I have insiders I can bug, and because it already  
 > supports hosted Bazaar branches.

IMO, this is an important advantage to Bazaar.  Similarly, the Debian
project sponsors a Mercurial host on Alioth, which I would imagine is
pretty professionally run.  Barry being an insider at Launchpad is a
good thing, though.  Does use of Launchpad imply access to the patch
queue manager, too?  Or is that Canonical-only?  (Not a problem if it
is Canonical-only, but it's a nice-to-have feature!)

 > Let me emphasis that Canonical is in no way driving this.

Good.  AFAICT, Canonical is a big business, it behaves like a big
business, but it talks like a charity.  Nothing wrong with the first
two, but the third confuses me.  I'd recommend keeping arms' length.

 > I personally think Bazaar+Launchpad will make some of our lives
 > easier,

+1 on that.  I've now done merges of multi-megabyte patches with both
Darcs and git.  It's thinkable.  Doing it with CVS or Subversion no
longer is.  (That would apply to bazaar, too, I'm sure, though I have
no experience with it.)

One caveat: as the dvcs proponents are always pointing out, it's not
necessary to actually use them in a distributed fashion.  In fact it's
*easy* to just drop them in to the same old workflow.  This gives a
perceptible improvement for insiders, but in open source you can get
lot more!  I hope, Barry, that you will allocate some time to
reorganizing the Mailman workflow to encourage participation from
third parties (eg, Fil, the MHonArc patch, etc).