From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id B44B6209AB for ; Wed, 6 Sep 2017 06:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750917AbdIFG20 (ORCPT ); Wed, 6 Sep 2017 02:28:26 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:54153 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750819AbdIFG20 (ORCPT ); Wed, 6 Sep 2017 02:28:26 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id E223A98D18; Wed, 6 Sep 2017 02:28:24 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=CPNtQNs1vaJ2N+pKw7RqOO2kDbM=; b=SL8fIE FHNEvivBe3FlxW6/26kSSUN1O27eYQw2CH/azxW/NKctNfr+ekfx5fYq2ohTigsB EHB4qPhePu/LticN7G2q5wH6ehb8ShuBNYF80rYXpj8Bt/1ok0SzJCLLY+YouGPT dB4uYCU2qU7q1FCrqT1D9zeOw6mu/eppjsxRc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=rhqyRzOgLTXvTdkbf8/Crp5rtYgVQwgV e6Pz6I74OCwZhUUyojZC4+pkenXDqwtT6S7zfx/uZAc412ynFF7McO83KI5iwL/r dQ0tBgkzRjisdEcFudKKxVYFWY+L/S7Yt/XKhAcfB4tis7POhQ+wiz2d3xpFlBV/ KVx8m80Zjqg= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id D705098D17; Wed, 6 Sep 2017 02:28:24 -0400 (EDT) Received: from pobox.com (unknown [104.132.0.95]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id 377E098D15; Wed, 6 Sep 2017 02:28:24 -0400 (EDT) From: Junio C Hamano To: Jonathan Nieder Cc: Linus Torvalds , Git Mailing List , Stefan Beller , bmwill@google.com, jonathantanmy@google.com, Jeff King , David Lang , "brian m. carlson" Subject: Re: RFC v3: Another proposed hash function transition plan References: <20170304011251.GA26789@aiede.mtv.corp.google.com> <20170307001709.GC26789@aiede.mtv.corp.google.com> Date: Wed, 06 Sep 2017 15:28:23 +0900 In-Reply-To: <20170307001709.GC26789@aiede.mtv.corp.google.com> (Jonathan Nieder's message of "Mon, 6 Mar 2017 16:17:09 -0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: 95D92B86-92CC-11E7-A022-FE4B1A68708C-77302942!pb-smtp1.pobox.com Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Jonathan Nieder writes: > Linus Torvalds wrote: >> On Fri, Mar 3, 2017 at 5:12 PM, Jonathan Nieder wrote: > >>> This document is still in flux but I thought it best to send it out >>> early to start getting feedback. >> >> This actually looks very reasonable if you can implement it cleanly >> enough. > > Thanks for the kind words on what had quite a few flaws still. Here's > a new draft. I think the next version will be a patch against > Documentation/technical/. Can we reboot the discussion and advance this to v4 state? > As before, comments welcome, both here and inline at > > https://goo.gl/gh2Mzc I think what you have over there looks pretty-much ready as the final outline. One thing I still do not know how I feel about after re-reading the thread, and I didn't find the above doc, is Linus's suggestion to use the objects themselves as NewHash-to-SHA-1 mapper [*1*]. It does not help the reverse mapping that is needed while pushing things out (the SHA-1 receiver tells us what they have in terms of SHA-1 names; we need to figure out where we stop sending based on that). While it does help maintaining itself (while constructing SHA3-content, we'd be required to find out its SHA1 name but the SHA3 objects that we refer to all know their SHA-1 names), if it is not useful otherwise, then that does not count as a plus. Also having to bake corresponding SHA-1 name in the object would mean mistakes can easily propagate and cannot be corrected without rewriting the history, which would be a huge downside. So perhaps we are better off without it, I guess. [Reference] *1*