From mboxrd@z Thu Jan 1 00:00:00 1970 From: A Large Angry SCM Subject: Re: [PATCH] Additional merge-base tests Date: Wed, 05 Jul 2006 09:15:18 -0700 Message-ID: <44ABE596.40103@gmail.com> References: <44A9E6AE.10508@gmail.com> <7v3bdhoraa.fsf@assigned-by-dhcp.cox.net> <44AA0DAE.1060308@gmail.com> <7vpsgllsnp.fsf@assigned-by-dhcp.cox.net> <7v8xn9gjh5.fsf@assigned-by-dhcp.cox.net> <44AAF49F.6090008@gmail.com> Reply-To: gitzilla@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: git@vger.kernel.org, Junio C Hamano X-From: git-owner@vger.kernel.org Wed Jul 05 18:15:48 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 1FyA2H-0004aM-7U for gcvg-git@gmane.org; Wed, 05 Jul 2006 18:15:33 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964820AbWGEQPY (ORCPT ); Wed, 5 Jul 2006 12:15:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964860AbWGEQPY (ORCPT ); Wed, 5 Jul 2006 12:15:24 -0400 Received: from nz-out-0102.google.com ([64.233.162.207]:18487 "EHLO nz-out-0102.google.com") by vger.kernel.org with ESMTP id S964820AbWGEQPW (ORCPT ); Wed, 5 Jul 2006 12:15:22 -0400 Received: by nz-out-0102.google.com with SMTP id m7so930439nzf for ; Wed, 05 Jul 2006 09:15:21 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:disposition-notification-to:date:from:reply-to:user-agent:x-accept-language:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding; b=W0Jz3+SL9i20YrZuA6qAbvzJE3Z41ZHNNXW8R/bDUx45Z6l+MMCFu+xw7azR/EwQSr83X0k5/721cq1hoRMJqW2eLKPN3AkDpACIxolO4xVF8IdirFFb+N3X4TPnOorRACtJ1cfRqed8xjZ6vdWdLRaz9KeipUciFS+J2mtHAoo= Received: by 10.65.205.7 with SMTP id h7mr5561022qbq; Wed, 05 Jul 2006 09:15:21 -0700 (PDT) Received: from ?10.0.0.6? ( [69.160.147.208]) by mx.gmail.com with ESMTP id d5sm2694707qbd.2006.07.05.09.15.20; Wed, 05 Jul 2006 09:15:20 -0700 (PDT) User-Agent: Mozilla Thunderbird 1.0.8 (X11/20060411) X-Accept-Language: en-us, en To: Johannes Schindelin In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: Johannes Schindelin wrote: > Hi, > > On Tue, 4 Jul 2006, A Large Angry SCM wrote: > >> Johannes Schindelin wrote: >>> Hi, >>> >>> On Tue, 4 Jul 2006, Junio C Hamano wrote: >>> >>>> Johannes Schindelin writes: >>>> >>>>> We could introduce a time.maximumSkew variable, and just walk only that >>>>> much further when traversing the commits. >>>> We could have had "commit generation number" in the commit >>>> object header, and use that instead of commit timestamps for >>>> these traversal purposes. The generation number for a commit is >>>> defined to be max(generation number of its parents)+1 and we >>>> prime the recursive this definition by defining the generation >>>> number for the root commit to be one. >>> Are you really, really sure this is a remedy? I, for one, am quite sure of >>> the opposite. What you propose is just another time scale, only this time, >>> it is not universally true (not even minus local incompetence to keep the >>> clock accurate). >> It works[*] and it does what using the timestamp was trying to do. Namely, >> work from "more recent" (or "closer") commits toward "older" (or "farther") >> commits until you've gone past the point you care about. >> >> It's a little late to be changing the structure of a commit and you'd have to >> deal with some size/scale issues, but it's do-able. A better idea may be to >> generate and keep the generation number on a per repository basis, and you'd >> be able to work around changing grafts. > > Like, inside the cache? I dunno. IMHO it is way too late to change the > structure of a commit in that particular manner, _plus_ you would get > overflow issues. Your don't need to change the commit object, create some repository specific, local, auxiliary information. Overflow should not be a problem until a path length to a root commit exceeds the machine word size. But is it really worth the work? Does it help anything other than merge-base? >> [*] Grafts do _really_ nasty things to this. Just like clock skew does now. > > Grafts can do much nastier things to you, for example having a circular > history. _But_ they cannot do that nasty thing outside of your repo. Clock > skews can. If grafts in your repository create a cycle, the misbehavior of merge-base should be among the least of your concerns.