From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.3 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_NONE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 2833E1F462 for ; Thu, 23 May 2019 20:53:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387809AbfEWUxO (ORCPT ); Thu, 23 May 2019 16:53:14 -0400 Received: from thyrsus.com ([71.162.243.5]:55586 "EHLO snark.thyrsus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387533AbfEWUxO (ORCPT ); Thu, 23 May 2019 16:53:14 -0400 Received: by snark.thyrsus.com (Postfix, from userid 1000) id 806E74704887; Thu, 23 May 2019 16:53:13 -0400 (EDT) Date: Thu, 23 May 2019 16:53:13 -0400 From: "Eric S. Raymond" To: Jonathan Nieder Cc: Jakub Narebski , git@vger.kernel.org Subject: Re: RFC: Separate commit identification from Merkle hashing Message-ID: <20190523205313.GB69096@thyrsus.com> Reply-To: esr@thyrsus.com References: <20190521013250.3506B470485F@snark.thyrsus.com> <86h89lq96v.fsf@gmail.com> <20190523200929.GA70860@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190523200929.GA70860@google.com> Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy User-Agent: Mutt/1.10.1 (2018-07-13) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Jonathan Nieder : > In other words, usually the benefit of supporting multiple hash > functions as a reader is that you want the strength of the strongest > of those hash functions and you need a migration path to get there. > If you don't have a way to eventually drop support for the weaker > hashes, then what benefit do you get from supporting multiple hash > functions? Not losing the capability to verify old parts of histories up to the strength of the old hash algorithm. Not perfect, but better than nothing. -- Eric S. Raymond