From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: VCS comparison table Date: Sat, 21 Oct 2006 14:04:56 -0700 (PDT) Message-ID: References: <9e4733910610140807p633f5660q49dd2d2111c9f5fe@mail.gmail.com> <45345AEF.6070107@utoronto.ca> <200610171030.35854.jnareb@gmail.com> <20061017073839.3728d1e7.seanlkml@sympatico.ca> <20061021141328.GE29843@artax.karlin.mff.cuni.cz> <845b6e870610210919i6d086654g3881343e6a3c9f84@mail.gmail.com> Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="21872808-1023987002-1161464696=:3962" Cc: Sean , Jan Hudec , bazaar-ng@lists.canonical.com, git@vger.kernel.org, Matthieu Moy , Jakub Narebski X-From: git-owner@vger.kernel.org Sat Oct 21 23:05:21 2006 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by ciao.gmane.org with esmtp (Exim 4.43) id 1GbO1w-0001c0-BK for gcvg-git@gmane.org; Sat, 21 Oct 2006 23:05:20 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423433AbWJUVFR (ORCPT ); Sat, 21 Oct 2006 17:05:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423428AbWJUVFR (ORCPT ); Sat, 21 Oct 2006 17:05:17 -0400 Received: from smtp.osdl.org ([65.172.181.4]:36059 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1161062AbWJUVFO (ORCPT ); Sat, 21 Oct 2006 17:05:14 -0400 Received: from shell0.pdx.osdl.net (fw.osdl.org [65.172.181.6]) by smtp.osdl.org (8.12.8/8.12.8) with ESMTP id k9LL4vaX009669 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Sat, 21 Oct 2006 14:04:58 -0700 Received: from localhost (shell0.pdx.osdl.net [10.9.0.31]) by shell0.pdx.osdl.net (8.13.1/8.11.6) with ESMTP id k9LL4u4T001323; Sat, 21 Oct 2006 14:04:57 -0700 To: =?ISO-8859-1?Q?Erik_B=E5gfors?= In-Reply-To: <845b6e870610210919i6d086654g3881343e6a3c9f84@mail.gmail.com> X-Spam-Status: No, hits=-0.48 required=5 tests=AWL X-Spam-Checker-Version: SpamAssassin 2.63-osdl_revision__1.95__ X-MIMEDefang-Filter: osdl$Revision: 1.155 $ X-Scanned-By: MIMEDefang 2.36 Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --21872808-1023987002-1161464696=:3962 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT On Sat, 21 Oct 2006, Erik Bågfors wrote: > > bzr is a fully decentralized VCS. I've read this thread for quite some > time now and I really cannot understand why people come to this > conclusion. Even the bzr people agree, so what's not to understand? The revision numbers are totally unstable in a distributed environment _unless_ you use a certain work-flow. And that work-flow is definitely not "distributed" it's much closer to "disconnected centralized". Now, you could be truly distributed: BK used the same revision numbering thing, but was distributed. But BK didn't even try to claim that their revision numbers were "simple" and that fast-forwarding is sometimes the wrong thing to do. So BK always fast-forwarded, and the revision numbers were just randomly changing numbers. They weren't stable, they weren't simple, and nobody claimed they were. So bzr can bite the bullet and say: "revision numbers are changing and meaningless, and we should just fast-forward on merges", or you should just admit that bzr is really more about "disconnected operation" than truly distributed. You can't have your cake and eat it too. Truly distributed _cannot_ be done with a stable dotted numbering scheme (unless the "dotted numbering scheme" is just a way to show a hash like git does - so the numbering has no _sequential_ meaning). Btw, this isn't just an "opinion". This is a _fact_. It's something they teach in any good introductory course to distributed algorithms. Usually it's talked about in the context of "global clock". Anybody who thinks that there exists a globally ticking clock in the system (and stably increasing dotted numbers are just one such thing) is talking about some fantasy-world that doesn't exist, or a world that has nothing to do with "distributed". Linus --21872808-1023987002-1161464696=:3962--