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=-0.8 required=3.0 tests=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 208DAC10DCE for ; Thu, 12 Mar 2020 19:30:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2410206E2 for ; Thu, 12 Mar 2020 19:30:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="F1V+rjtS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbgCLT37 (ORCPT ); Thu, 12 Mar 2020 15:29:59 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:43933 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726310AbgCLT36 (ORCPT ); Thu, 12 Mar 2020 15:29:58 -0400 Received: by mail-oi1-f193.google.com with SMTP id p125so6718644oif.10 for ; Thu, 12 Mar 2020 12:29:56 -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=xQAnlU7ew4ToZ2m+fwY2CiO1K5S/P+QKuSFwJKlmnWI=; b=F1V+rjtSlpd1X3ONvo4ALCf1qgSIsoUleVhWQnvc6xDlFz4TzN20YxkfEI+1vWE/3n zZc9DE/AHxLryfd5z09pzkA4z5ARwnlX/RfiumzPIl2kg16ajN3chlxibm2osZ9fENVf wUBKQIWyclATNzVpfuiOc67LYjrsoxiUVBW9VFNNgSKL/GZlwfQ+j+LIeeua68lw6Qto I+ywfbpKUtC5UbaEuz8Ax7/cmzS/lzLUuH0HKlAJXcidtZy0hUnielsj5GtprUUUGawG 89m5cp8i0eeSgLD5XwGqClx6JH3ZO2ZUXHDEj4aaIzXASMLDQUmQIxl2LMnL8qlNghdI 6Wtg== 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=xQAnlU7ew4ToZ2m+fwY2CiO1K5S/P+QKuSFwJKlmnWI=; b=kPo9BtQzqkxoiKxk8hhDQaBpEb7kYO9PtZnhBfJFsEroEMlFfdHR1XiiJBqCvgfvnr yiVozGWizgTq/+akQV88yy4QFLl0Y1b/USsWFLLrN40b9Xue3lBdr0X5tJ/0kyZ3dm0g uMkCpXXuhmxgB+8lcmLwV4C2qoeSDRjie8QEV9hPZebwNR7R5crTJ7SP8EwuUpOnk0Dj 0h7TBbtXLaHItjTUjXEtzhGRFV5w7okOLumpiYRfZm/F/AgLDAclvHfy0BSzptWw2J5k X+SVbGPplmZ5hfx2YaiUn9E7wSdwOxwKR/sSGvAd2vr11okb/Kb7MOAdauqR8hsAe8vS KJSQ== X-Gm-Message-State: ANhLgQ0EGpKwUUNiSP57dnrT86+2gkEPNwfXGpo5G2egnNFod0J42X72 BOSpMtT5vvidDDugDoG1ME2XDiMer6N0jLrTSN8= X-Google-Smtp-Source: ADFU+vsqy/nb3w6d0WogiWij8Gm+ZqkGCY32Z7PlPlXcrm42kMcVzcteOS3Jz2GqOs3L7Ta5DXEs1udgY0v3Asd2YWE= X-Received: by 2002:aca:dc45:: with SMTP id t66mr4031243oig.39.1584041396158; Thu, 12 Mar 2020 12:29:56 -0700 (PDT) MIME-Version: 1.0 References: <20200312151318.GM212281@google.com> In-Reply-To: From: Elijah Newren Date: Thu, 12 Mar 2020 12:29:45 -0700 Message-ID: Subject: Re: [PATCH v5 20/20] rebase: rename the two primary rebase backends To: Junio C Hamano Cc: Emily Shaffer , Elijah Newren via GitGitGadget , Git Mailing List , Jeff King , Johannes Schindelin , Phillip Wood , Denton Liu , Pavel Roskin , Alban Gruin , =?UTF-8?Q?SZEDER_G=C3=A1bor?= , Jonathan Nieder Content-Type: text/plain; charset="UTF-8" Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Thu, Mar 12, 2020 at 12:12 PM Junio C Hamano wrote: > > Elijah Newren writes: > > > On Thu, Mar 12, 2020 at 8:13 AM Emily Shaffer wrote: > >> ... > >> This broke quite a few upstream users for us today... > > One more thing I've been wondering was if we should really have said > "ok, the two known gotchas have been dealt with, so let's ship it". > It is quite likely that users may be hit by remaining differences > between the merge and apply backends that we assume to be merely > subtle and easy-to-work-around ones, and it may be prudent to use > the "let's not change the default just yet, but ask people to test > it in their workflow by advertising the configuration" patch. Good question, but there's several things to unpack here... First, note that this particular breakage would have occurred regardless of the default setting, because the problem was that they setting rebase.backend to an unrecognized value, not that we used a different backend than they were used to. Second, for the particular case of the post-commit hook that they referenced in their rationale, that item was documented near the end of the 2.25 cycle and mentioned in previous patchsets[1, 2] so I figured this case was already considered. Those two points may obscure the issue, though; your question is still valid. I think the bigger question is whether there are other unknown differences, or even known differences that are a bigger issue than we currently realize. That's hard to judge, and it may not be possible to judge until we've flipped the default. As such, it's a judgement call. I can see the judgement call going either way. A couple things to weigh in on how to go: - Making rebase.backend default to 'apply' for 2.26 is certainly the conservative option and may give us more feedback and time to iron out differences - We had multiple complaints this cycle about rebase.backend=apply merging things incorrectly with the only workaround being to use the merge backend[3,4] - The rebase-backend topic wasn't merged down to master until less than a week before -rc0. (For a variety of reasons.) A big change like this probably would have been better to merge down earlier in some cycle. To be honest, if I was maintainer, I'm not sure which direction I'd pick. If you feel safer switching the default backend to apply for this cycle and then (re-)revert it early next cycle to the merge backend, I think that's totally reasonable. [1] https://lore.kernel.org/git/pull.679.v4.git.git.1579155273.gitgitgadget@gmail.com/ [2] https://lore.kernel.org/git/CABPp-BHONuRyt8VJqRuoCF2rGYZ5EhH9KJXQZ3NO69rYwA5J3g@mail.gmail.com/ [3] https://lore.kernel.org/git/CABPp-BGiu2nVMQY_t-rnFR5GQUz_ipyEE8oDocKeO+h+t4Mn4A@mail.gmail.com/ [4] https://lore.kernel.org/git/20200108223557.GE32750@szeder.dev/