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: AS53758 23.128.96.0/24 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS,URIBL_CSS, URIBL_CSS_A shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 82FB91F670 for ; Sun, 24 Oct 2021 05:16:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230149AbhJXFSU (ORCPT ); Sun, 24 Oct 2021 01:18:20 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:59564 "EHLO pb-smtp1.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229464AbhJXFSU (ORCPT ); Sun, 24 Oct 2021 01:18:20 -0400 Received: from pb-smtp1.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 685B5100A59; Sun, 24 Oct 2021 01:15:57 -0400 (EDT) (envelope-from junio@pobox.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=7zKsnOUM1vMX/Va/fZcElSVMbugtPycEKlG4nf zzz2M=; b=kAGVrBCASt59RH+GRorp9n/9IvfIZ9uQm8fseUFhPuynRmWa/n/tyn WBvHckcy1llb3epZjO8vGN29VdGqBFC3qcjRCURoYIYA4Z6jRGjdDoAdgLpzGNLl woJ+x6E8l6jyC6rsP6S0DMToRhtDQWoxKyeEIKrximKUC2T/Ndi1U= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 5FA69100A58; Sun, 24 Oct 2021 01:15:57 -0400 (EDT) (envelope-from junio@pobox.com) Received: from pobox.com (unknown [104.133.2.91]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id C8705100A57; Sun, 24 Oct 2021 01:15:56 -0400 (EDT) (envelope-from junio@pobox.com) From: Junio C Hamano To: Eli Schwartz Cc: git@vger.kernel.org, =?utf-8?Q?Ren=C3=A9?= Scharfe Subject: Re: [PATCH 3/3] pretty: add abbrev option to %(describe) References: <20211024014256.3569322-1-eschwartz@archlinux.org> <20211024014256.3569322-4-eschwartz@archlinux.org> Date: Sat, 23 Oct 2021 22:15:55 -0700 In-Reply-To: <20211024014256.3569322-4-eschwartz@archlinux.org> (Eli Schwartz's message of "Sat, 23 Oct 2021 21:42:56 -0400") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: 77E5CE3C-3489-11EC-8B07-62A2C8D8090B-77302942!pb-smtp1.pobox.com Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Eli Schwartz writes: > The %(describe) placeholder by default, like `git describe`, uses a > seven-character abbreviated commit hash. This may not be sufficient to "hash" -> "object name". > fully describe all git repos, resulting in a placeholder replacement "all git repos" -> "all commits in a given repository" (there may be other valid way to clarify, but the point is that 'describe' does not describe 'git repos' in the sense that my repository gets description X while your repository gets description Y). > changing its length because the repository grew in size. This could > cause the output of git-archive to change. > > Add the --abbrev option to `git describe` to the placeholder interface > in order to provide tools to the user for fine-tuning project defaults > and ensure reproducible archives. Note that it is sad that --abbrev= does not necessarily ensure reproducibility. To be more precise, I do not think it sacrifices uniqueness to make the output reproducible. You can get more than N hex-digits in the output if N is too small to ensure uniquness. So it indeed is that this line of thought ... > One alternative would be to just always specify --abbrev=40 but this may > be a bit too biased... ... to use --abbrev=999 (because 40 is not the length of a full object name in the SHA-2 world) is the only reasonable way, if what you care about is the reproducibility. Side note. I think "git describe --no-abbrev" is buggy in that it does not give a full object name; I didn't check the code, but it appears to be behaving the same way as "git describe --abbrev=0" (show no hexdigits). Fixing this bug may possibly be a low-hanging fruit. But even if the feature cannot be used to guarantee a full reproducibility, it is a good thing that we can now add this feature with minimum effort thanks to the previous two steps. The refactoring I suggested in my review for the previous step will shine, if we want to do a good job parsing the --abbrev= option, since such a code organization would make it a fairly easy addition to introduce "integer" type that calls match_placeholder_arg_value() to read the option value (like "string" does) and validate that the value is indeed an integer. Would we want to support "--contains" as another boolean type? How about "--all" and "--long"? All three sound plausible candidates. Thanks.