Tom Lord's Decentralized Revision Control System

Bruce Perens writes: "He'll have to change its name, but Tom Lord's arch revision control system is revolutionary. Where CVS is a cathedral, 'arch' is a bazaar, with the ability for branches to live on separate servers from the main trunk of the project's development. Thus, you can create a branch without the authority, or even the cooperation, of the managers of the main tree. A global name-space makes all revision archives worldwide appear as if they are the same repository. Using this system, most of what we do using 'patch' today would go away -- we'd just choose, or merge, branches. Much of the synchronization problem we have with patches is handled by tools that eliminate and/or manage conflicts -- they solve some of the thorny graph topology issues around patch management. Arch also poses its own answer to the 'Linus Doesn't Scale' problem. This is well worth checking out." If you're asking "What about subversion?", well, so is Tom.

Comments

Subversion or Arch or both?

[kfogel]

I hope both systems (Arch and Subversion) get some widespread use. Like a lot of Subversion developers, I'm genuinely curious to see a) how well the Arch model works in practice, and b) how well Arch's implementation of that model works out. If it turns out to be winning, then that'll be a big step forward for collaborative projects & free software. Arch sounds a lot like Bitkeeper only without the license problems, and I've talked to some happy Bitkeeper users before (a small sample, so it's hard to know whether we're dealing with a Shift To Better Paradigm or just good software).

Subversion was deliberately designed to address CVS's shortcomings, not to break new ground. Our philosophy was essentially conservative: CVS basically works, but has some bugs and maintainability problems. Let's keep the model and fix the problems. Result: Subversion.

The ideal situation is a world where both models have good, free implementations. Then we'll all very quickly find out which model works better. :-)

-Karl

Neither funny nor accurate

[William Tanksley]

I'm surprised this one got modded up. The poster clearly knows nothing about the topic; it's just an ignorant flame.

In case anyone's wondering, arch supports and uses write permissions; however, it also allows you to start your OWN server, and people can hook up to it in parallel with the main server, and get all the branches which appear on either.

You can commit all the crashy code you want on your own server, but it won't affect anyone who isn't using your server.

The genius is that your server is hooked up to the original server, live, and you can track the changes they make, merging when and where you like. If the project manager for the original server feels like it (and if you let him), he can track the changes on your server as well. If someone else has started their own branch server, you can merge directly with them as well.

VERY clever.

Although I don't dig the Subversion trashing; Subversion is also very cool for its own purposes. I'm glad Tom took the time to underline the differences, but I'm unhappy that the result is so slanted. It didn't need to be: both arch and Subversion stand on their own as superb projects, and there's even another one coming out of IBM "sometime" which has its own merits.

-Billy