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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43D7FC4338F for ; Tue, 3 Aug 2021 17:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3133460F0F for ; Tue, 3 Aug 2021 17:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237540AbhHCRBn (ORCPT ); Tue, 3 Aug 2021 13:01:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237576AbhHCQ6m (ORCPT ); Tue, 3 Aug 2021 12:58:42 -0400 Received: from mail-oo1-xc31.google.com (mail-oo1-xc31.google.com [IPv6:2607:f8b0:4864:20::c31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 783D7C061385 for ; Tue, 3 Aug 2021 09:57:24 -0700 (PDT) Received: by mail-oo1-xc31.google.com with SMTP id k7-20020a4abd870000b029025e4d9b0a3dso1600666oop.6 for ; Tue, 03 Aug 2021 09:57:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Z2y91Yk8iJMgaz2JjB+rz0jkUPa1hNXaDYkacHIAvog=; b=UEIV0T3/VUM0eBP181XQP7fUhSepDLc4tjyWZHgtdJnnF5B38L2J5wtwNsskWJSwtg 8Km1f3GQ0qO52ty3rkJBo8w7LZ4uIwE7U/ONRtbNMsyfIdRV/TSu7x9uLTzclX5WaWsZ zKOvfsNvGODy5WVuhxRSumaNvtYeazaXT8s9vOsqrQDkkJ4+U9C2cbnzFqMb/JLTQzj8 dj4si1WKrOSHF3ShVg8h/iN8tUgZWiT+WBTX91RUlUgv7nTZzozWKp+GIZxJRASaTXYm hwuifJv5iX7qSqNni5zqpo/8AztaTvzcDibAFi7JCz2GNNYOzW19Rzq5ZLEPN0YaOkQx Ivgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Z2y91Yk8iJMgaz2JjB+rz0jkUPa1hNXaDYkacHIAvog=; b=YUHMDuDGxquF/MlA2NUrYq+xMANTB9RLU2JphLBNS870v2DAiYQPiAXvRo3DhAYuhg jA0y8vFnfil0ljAN9hZs0ExDtwkYA8xrMIToNcy2X4/aupRmI3xjZGiuBfibfnn4uXdx 4GlbGguMe+3hm+owmhLXxUwjhLOtG9kWNYwtuF80+7V/apL2qMxRLsQO3Sx4uNHtz4Mw XdYSE5nVFsyq1eeeUnF1MM7BWgj4pCcA9Cj2BvwWG1J2HiSU1MiLYVhL9X/kJxi9jXNn lPaftXQD4KCaqYWpcsCqrAy/56bPgXcOCJ+ljQXy6TQKKpsuhKogoOWfe915zStqj3E2 qnBw== X-Gm-Message-State: AOAM533VbAr/00rAtKvMVdle64KQ0Dtz+4to7qezzFhjbUHHUUFA0kK1 Am0crz82qzDsZYKOXY0NaQCcKmxbXYzOU/zn/vQ= X-Google-Smtp-Source: ABdhPJxnOClvAWvD0QWrxyGUpZfohItfhdUCnHZH8HqHpi2uXv2Oq30Jo6RNEejxUm/K+O12Og+iq1LByUc9wz3rWnw= X-Received: by 2002:a4a:d40a:: with SMTP id n10mr15089436oos.32.1628009843827; Tue, 03 Aug 2021 09:57:23 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Elijah Newren Date: Tue, 3 Aug 2021 10:57:12 -0600 Message-ID: Subject: Re: [PATCH 0/2] [RFC] Switch default merge backend from recursive to ort To: Jeff King Cc: Elijah Newren via GitGitGadget , Git Mailing List , Christian Couder , Derrick Stolee , Emily Shaffer , Eric Sunshine , Johannes Schindelin , Jonathan Nieder , Jonathan Tan , Junio C Hamano , Phillip Wood , =?UTF-8?Q?Ren=C3=A9_Scharfe?= , Taylor Blau , =?UTF-8?B?w4Z2YXIgQXJuZmrDtnLDsCBCamFybWFzb24=?= Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Tue, Aug 3, 2021 at 9:56 AM Jeff King wrote: > > On Sun, Aug 01, 2021 at 12:07:39AM +0000, Elijah Newren via GitGitGadget wrote: > > > This is an RFC series designed to spur feedback about switching the default > > merge backend (reviewing the patches is of secondary importance at this > > point). Some questions: > > > > * Are there things others want before this series is considered for > > inclusion? > > * What kind of timeline do others think is reasonable? > > * Would it be beneficial to let this series sit in 'next' for an extended > > duration to gain more feedback? > > It looks like others gave some more specific review on the patches, but > on the meta-topic of "do we switch, and when", my response is: yes, and > soon. :) > > Having watched the development of merge-ort, plus all of the weird > corner cases in merge-recursive we've seen over the years (many of which > you found and added tests for while working on merge-ort!), my gut > feeling is that the switch is _much_ more likely to fix problems people > might see in the wild rather than cause them. > > It would make sense to me to do the switch in 'next' early in the > post-v2.33 cycle. It can cook there for a bit, but I think we have found > that it's much more likely to see actual use once it hits 'master'. So I > don't see a particular reason to have it sit in 'next' for a long time. > We should get as much exposure in 'master' during the v2.34 cycle as > possible. > The nice thing is that the two strategies can co-exist. So if it does > turn out to have any regressions, it's an easy revert to switch back, > and even post-release users can switch at runtime. We have pull.twohead, > but I don't think we have an equivalent that would impact a bare "git > merge" or "git rebase -m". Maybe it would be worth adding those as an > escape hatch? Actually, pull.twohead is not pull specific; it already affects merge, rebase (-m is the default for rebase, btw), cherry-pick, and revert. pull.twohead has affected a bare "git merge" since 1c7b76be7d ("Build in merge", 2008-07-07). I thought it was weird that "merge strategy" for the merge command was specified via a config option under "pull", and included my misgivings about it in the commit message of 14c4586c2d ("merge,rebase,revert: select ort or recursive by config or environment", 2020-11-02) when I made sequencer.c pay attention to that config option as well: """ Also, allow folks to pick the new algorithm via config setting. It turns out builtin/merge.c already had a way to allow users to specify a different default merge algorithm: pull.twohead. Rather odd configuration name (especially to be in the 'pull' namespace rather than 'merge') but it's there. Add that same configuration to rebase, cherry-pick, and revert. """ But no one had an alternate suggestion or opinion on attempting to migrate the configuration to a different name, so it has just stuck. Anyway, if folks want to try out 'ort' with the 2.32 or 2.33 releases, they can set pull.twohead=ort. Once we switch the default, they can set pull.twohead=recursive to get the old default.