From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81134C433EF for ; Tue, 12 Oct 2021 20:37:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58CF7610C9 for ; Tue, 12 Oct 2021 20:37:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234047AbhJLUj0 (ORCPT ); Tue, 12 Oct 2021 16:39:26 -0400 Received: from pb-smtp2.pobox.com ([64.147.108.71]:60989 "EHLO pb-smtp2.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233690AbhJLUjZ (ORCPT ); Tue, 12 Oct 2021 16:39:25 -0400 Received: from pb-smtp2.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 54D641015F7; Tue, 12 Oct 2021 16:37:23 -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:content-transfer-encoding; s=sasl; bh=eed2HTux5QiU vgGxL8L5NKY/Pliz4C7BeiI9AoEuXc4=; b=gykkhWi84vv6Dzz0HSQg3DDm1xCC hsFeBLNbfYoeh6ANzkkyVEdRVxD6F1ZtnbOIqY3P1J7jqY2vZYzGIn9nwkQNoI3U M0QGQc91gT6tXZELFw3fAe2bZu0OuzHghX821IJqTwxugeCU1K2hk52L92kjWXb3 vM30fWZqqMDpxyY= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 4C1AA1015F6; Tue, 12 Oct 2021 16:37:23 -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-smtp2.pobox.com (Postfix) with ESMTPSA id A140B1015F4; Tue, 12 Oct 2021 16:37:22 -0400 (EDT) (envelope-from junio@pobox.com) From: Junio C Hamano To: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason Cc: =?utf-8?Q?Ren=C3=A9?= Scharfe , git.mexon@spamgourmet.com, git@vger.kernel.org Subject: Re: [PATCH] add: don't write objects with --dry-run References: <0131d21f-dabd-3da5-34bd-a570e990f9e0@web.de> <871r4qj8mw.fsf@evledraar.gmail.com> Date: Tue, 12 Oct 2021 13:37:21 -0700 In-Reply-To: <871r4qj8mw.fsf@evledraar.gmail.com> (=?utf-8?B?IsOGdmFyIEFy?= =?utf-8?B?bmZqw7Zyw7A=?= Bjarmason"'s message of "Tue, 12 Oct 2021 22:17:06 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 X-Pobox-Relay-ID: 33DF9C90-2B9C-11EC-9F96-CD991BBA3BAF-77302942!pb-smtp2.pobox.com Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason writes: > I think the "git fetch --dry-run" command behaves like this too, > i.e. doesn't update refs, but fetches and writes objects. > > For the patch I hacked up I think it's easy to argue that it shouldn't > do compression etc. > > For this sort of thing and "fetch" I'm not so sure. Do we really know > that there aren't people who rely on this for say the performance of > seeing what an operation would do, and then not pay as much for the > "real one" that updates the index/refs/etc. later? Is that subsequent > "fetch" cheaper because of the --dry-run? The answer to the last one is an easy "yes". Trying to gauge the time it would take for a real fetch with "--dry-run" is a losing battle, I would think, as the pre-fetching would make the "real" one cheaper, so from that point of view, I think we can ignore those who time "--dry-run" and try to figure out anything meaningful. This in any case is an interesting area, as the definition of correctness of what "dry-run" does can be quite fuzzy. As long as it does not change the index, "git add --dry-run", even if it writes objects or detects filesystem corruption by noticing I/O error while compressing the data taken from the working tree files, is still correct and the patch in question is not technically a bugfix (it is a performance thing). "git fetch --dry-run" would fall into the same category, so would "git hash-object" without "-w". All can use performance enhancement without breaking existing users, I would think. Thanks.