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=-2.7 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, URIBL_BLOCKED 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 216ADC433EF for ; Sun, 5 Sep 2021 10:05:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1EE860FE6 for ; Sun, 5 Sep 2021 10:05:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237562AbhIEKGh (ORCPT ); Sun, 5 Sep 2021 06:06:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237534AbhIEKGh (ORCPT ); Sun, 5 Sep 2021 06:06:37 -0400 Received: from mail-qk1-x729.google.com (mail-qk1-x729.google.com [IPv6:2607:f8b0:4864:20::729]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F3DEC061575 for ; Sun, 5 Sep 2021 03:05:34 -0700 (PDT) Received: by mail-qk1-x729.google.com with SMTP id ay33so3852225qkb.10 for ; Sun, 05 Sep 2021 03:05:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=o2s5RCDj1flJaphCyks4o/McKwAb2xoJFGbVoKDnu3A=; b=BCBkJmKKo4Ej2y0uOhXf0wxZbk08rGhTRRczlPJX+vIXTErL+35Dnu6OQy+lQdpULi esmyPZznZu60ulhYUpTPdR86OV5VhX3U395bFtL4CB77+/O2Ug7rzusCwj4lb+qUzX/C kLpNPHkEXBlMHLeZZmL4Giq4hZsOguLWJUy0J3pPsF2NhyiN35uKD0ex9OdWUMwg08Fa O6jzDQBOuTxR3AtXaS42Jp94nmaxCsuntwyh+TqbQv5NUr3Rj1krLevmwCu1NF2b5+7Q L3mw9shSKEP8URzY5maDeE7poDTZtKfU4eRL2VNROI/x71nFABjNr8HRsAQXmIf5Vn/D s1lQ== 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:content-transfer-encoding; bh=o2s5RCDj1flJaphCyks4o/McKwAb2xoJFGbVoKDnu3A=; b=sO+TiASC4Hb14qa3xgzkV0MddWBkcv2+XF3AVC/r3VtkioOcjBcMJ14CsVAhjYuPtf vGZ+RywcvD8y8CbADHZwzJbmTIP14o+pOn0kcFo8WLbtyeH3mDeP7f+gPbytYghYl/Os fKt8jDFSDW7i1l4k6desrTdEkgf9lE7sJSNWtOrGlOxtUGyTI3HcLmg8Q99pY/O9uV5k rQvpAZBLQKHXVc+w+Oy8+jn01slp7UvBkRJFGhzx6KImfgwkTZGlIjWZQ7IiZgIrUPZe y1ePylNsX2qQskxpXG7bTwKcqSfVK+2ixNB+tDM6mOnsVoc/q6DveeRYnTfGmfYcvJ32 KxjA== X-Gm-Message-State: AOAM5327J3EuJVoqMw/ONqj9SthuNYba7pF1gilXj5d0cU5AKgNtfzdx nt1eKtslOrvNhJtt6UDrVKb4GSFWQ5qd/wvYc5Y= X-Google-Smtp-Source: ABdhPJyWgy7RN2iQvbzRZDIYnWWAixgH2Bo/YcXbc2a//y5SP2cEn3dt960K/KkrBsOXdp1ZoBZvYZ2sLsu3OQrCpbc= X-Received: by 2002:a05:620a:430f:: with SMTP id u15mr6469686qko.32.1630836333407; Sun, 05 Sep 2021 03:05:33 -0700 (PDT) MIME-Version: 1.0 References: <87sfyjpiu3.fsf@evledraar.gmail.com> In-Reply-To: <87sfyjpiu3.fsf@evledraar.gmail.com> From: Fedor Biryukov Date: Sun, 5 Sep 2021 12:05:22 +0200 Message-ID: Subject: Re: Aborting 'rebase main feat' removes unversioned files To: =?UTF-8?B?w4Z2YXIgQXJuZmrDtnLDsCBCamFybWFzb24=?= Cc: Elijah Newren , Jeff King , Bagas Sanjaya , Git Mailing List Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Had a brief look at the code. builtin/rebase.c is using rebase_head helper function defined in rebase.c/h to do a checkout. builtin/checkout.c does not use the rebase_head helper function. I would expect both to use the same code defined in checkout.c/h, but there is no such file. On Sun, Sep 5, 2021 at 9:44 AM =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason wrote: > > > On Sat, Sep 04 2021, Elijah Newren wrote: > > > On Sat, Sep 4, 2021 at 3:19 AM Jeff King wrote: > >> > >> On Sat, Sep 04, 2021 at 11:51:19AM +0200, Fedor Biryukov wrote: > >> > >> > There is no way this could be the intended behavior, but the good ne= ws > >> > is that I cannot reproduce it... > >> > Looks like it occurs only in one git version (2.31.0.windows.1, IIRC= ). > >> > And it does not occur in the latest git version: git version 2.33.0.= windows.2. > >> > >> I think it is a bug, and it seems to reproduce easily for me (with bot= h > >> the current tip of master, and with v2.33.0). Here's the recipe you > >> showed, with a little debugging at the end: > >> > >> set -x > >> git init repo > >> cd repo > >> git commit -m base --allow-empty > >> git checkout -b feat > >> echo feat >readme.txt > >> git add readme.txt > >> git commit -m txt=3Dfeat > >> git checkout main > >> echo precious >readme.txt > >> > >> cat readme.txt > >> git checkout feat > >> cat readme.txt > >> git rebase main feat > >> cat readme.txt > >> > >> This produces: > >> > >> + cat readme.txt > >> precious > >> + git checkout feat > >> error: The following untracked working tree files would be overwritt= en by checkout: > >> readme.txt > >> Please move or remove them before you switch branches. > >> Aborting > >> + cat readme.txt > >> precious > >> + git rebase main feat > >> Current branch feat is up to date. > >> + cat readme.txt > >> feat > >> > >> So git-checkout was not willing to overwrite the untracked content, bu= t > >> rebase was happy to obliterate it. > >> > >> It does the right thing in very old versions. Bisecting, it looks like > >> the problem arrived in 5541bd5b8f (rebase: default to using the builti= n > >> rebase, 2018-08-08). So the bug is in the conversion from the legacy > >> shell script to C (which makes sense; the shell version was just calli= ng > >> "git checkout", which we know does the right thing). > >> > >> -Peff > > > > Turns out this is quite a mess. It's also related to the "don't > > remove empty working directories" discussion we had earlier this > > week[1], because we assumed all relevant codepaths correctly avoided > > deleting untracked files and directories in the way. But they don't. > > And rebase isn't the only offender, because this is buried in > > unpack_trees. In fact, it traces back to (and before) > > fcc387db9b ("read-tree -m -u: do not overwrite or remove untracked > > working tree files.", 2006-05-17) > > which has additional commentary over at > > https://lore.kernel.org/git/7v8xp1jc9h.fsf_-_@assigned-by-dhcp.cox.net/= . > > It appears that before this time, git happily nuked untracked files > > and considered them expendable, in basically all cases. However, this > > patch continued considering them as expendable whenever opts->reset > > was true. There wasn't much comment about it at the time for the > > reasoning of how opts->reset was handled, though trying to read > > between the lines perhaps Junio was trying to limit the backward > > compatibility concerns of introducing new errors to fewer code paths? > > Anyway, Junio did mention `read-tree --reset` explicitly, but this > > opts->reset usage also occurs in am, checkout, reset -- and anything > > that calls the reset_head() function including: rebase, stash, > > sequencer.c, and add-patch.c. > > > > So, then...should we preserve untracked (and non-ignored) files in all > > these cases? This rebase case seems clear, but others might be less > > clear. For example, should "git reset --hard" nuke untracked files > > (what if it's a directory of untracked files getting nuked just to > > place a single file in the location of the directory)? The > > documentation isn't explicit, but after reading it I would assume that > > untracked files should be preserved. Since we've had bugs in "git > > reset --hard" before, such as requiring two invocations in order to > > clear out unmerged entries (see [2] and [3]), that also suggests that > > this is just another bug in the same area. But the bug has been > > around so long that people might be expecting it; our testsuite has > > several cases that incidentally do. Granted, it's better to throw an > > error and require explicit extra steps than to nuke potentially > > important work, but some folks might be unhappy with a change here. > > Similarly with "git checkout -f". > > > > And stash.c, which operates in that edge case area has tests with > > files nuked from the cache without nuking it from the working tree > > (causing the working tree file to be considered untracked), and then > > attempts to have multiple tests operate on that kind of case. Those > > cases look a bit buggy to me for other reasons (I'm still digging), > > but those bugs are kind of hidden by the untracked file nuking bugs, > > so fixing the latter requires fixing the former. And stash.c is a > > mess of shelling out to subcommands. Ick. > > > > I have some partial patches, but don't know if I'll have anything to > > post until I figure out the stash mess... > > I'd just like to applaud this effort, and also suggest that the most > useful result of any such findings would be for us to produce some new > test in t/ showing these various cases of nuking/clobbering and other > "non-precious" edge cases in this logic. See[1] and its linked [2] for > references to some of the past discussions around these cases. > > 1. https://lore.kernel.org/git/87a6q9kacx.fsf@evledraar.gmail.com/ > 2. https://lore.kernel.org/git/87ftsi68ke.fsf@evledraar.gmail.com/ > > > [1] https://lore.kernel.org/git/YS8eEtwQvF7TaLCb@coredump.intra.peff.ne= t/ > > [2] 25c200a700 ("t1015: demonstrate directory/file conflict recovery > > failures", 2018-07-31) > > [3] ad3762042a ("read-cache: fix directory/file conflict handling in > > read_index_unmerged()", 2018-07-31) >