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: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_NONE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 730BF1F45A for ; Thu, 15 Aug 2019 21:41:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732701AbfHOVlX (ORCPT ); Thu, 15 Aug 2019 17:41:23 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:45127 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732317AbfHOVlW (ORCPT ); Thu, 15 Aug 2019 17:41:22 -0400 Received: by mail-pf1-f193.google.com with SMTP id w26so1959933pfq.12 for ; Thu, 15 Aug 2019 14:41:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=VpESJshbUTcHuiOXL0DK9p2Uq7kbIywsc8gzFi+ifw8=; b=HQJ9t38+hYDMa50BMyYtWL8IJyPGakO/91YyyJgc6kyZ9R9x2RXkdsvwGHOY9fX24n YWjKsN020bBP5iSaWyrtCaiVPQ6nDUU6d2//ctG6XuIWjfI24Lc5uOUV/n3Spauy03GW bye9oyTKoAYIjy3OniGCj8L9bop1RrFjZgnjiNImlUc8wSgqWEqJOlrBRbwF+fB63l8k UX3zjd3HS2fgYh2Jec0ek69Hcob4v99Ijcmulona2ZFmzbnS9DFdEdIPirB5AgPHlDHZ hWzfj69f+Q72MOd37atO5EfPz1fUuU34XwckhBsk59/zoVm6X8DqUOlzbG81M/R4Didl ElMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=VpESJshbUTcHuiOXL0DK9p2Uq7kbIywsc8gzFi+ifw8=; b=VPHK6Y04o3K/Qi0USl9N4UjQ24l/VzW7BN0Rww9/gxLSY8G63sTIakDDlDiv/3oZr+ GdocJmgN4t0QIBcFtBvqdFNrCYMdiypbEb6FYH+Xu2t+ZOFnYTHzd+OuJ5uE9HSMaXhZ CyL+SSaCFXyMNA++xbPikuslikvQRq+RZsFPUCZYZ2A1uLGznhRXHRckWsI2xKBKqBev GGBuQPjyCZ6ZffkhXEZ8n3HDxezh4/kQdTDP+uNNQGYYtKgf6z2AajjkcL/WKt2Sn7A0 L0nJYJUzcLyxXNZNR/Mi2bUxUh0BnjkhMTHJMomkm6Xvu6UZVcXunCO7vET/jkQNilkD fO/w== X-Gm-Message-State: APjAAAUQvbQm2/YNM5d4JCRXfCQbN+jP20VB5liBMVOYEKcgesZe7FTS rGicR6ppOZ3EqiBRHhiZFS7M+ztw X-Google-Smtp-Source: APXvYqxHlrKVUbEpGJa5ICP7lgj0xdPUez//eb/jegIlxsvadqJO4ZY7gJIzGy39S1ClgXOSKRccZg== X-Received: by 2002:a63:195f:: with SMTP id 31mr5116011pgz.225.1565905281718; Thu, 15 Aug 2019 14:41:21 -0700 (PDT) Received: from newren2-linux.yojoe.local ([8.4.231.67]) by smtp.gmail.com with ESMTPSA id i124sm4131966pfe.61.2019.08.15.14.41.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 15 Aug 2019 14:41:21 -0700 (PDT) From: Elijah Newren To: git@vger.kernel.org Cc: Junio C Hamano , Johannes Schindelin , Derrick Stolee , Elijah Newren Subject: [PATCH v3 08/24] Ensure index matches head before invoking merge machinery, round N Date: Thu, 15 Aug 2019 14:40:37 -0700 Message-Id: <20190815214053.16594-9-newren@gmail.com> X-Mailer: git-send-email 2.23.0.rc2.32.g2123e9e4e4 In-Reply-To: <20190815214053.16594-1-newren@gmail.com> References: <20190726155258.28561-1-newren@gmail.com> <20190815214053.16594-1-newren@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org This is the bug that just won't die; there always seems to be another form of it somewhere. See the commit message of 55f39cf7551b ("merge: fix misleading pre-merge check documentation", 2018-06-30) for a more detailed explanation), but in short: builtin/merge.c contains this important requirement for merge strategies: ...the index must be in sync with the head commit. The strategies are responsible to ensure this. This condition is important to enforce because there are two likely failure cases when the index isn't in sync with the head commit: * we silently throw away changes the user had staged before the merge * we accidentally (and silently) include changes in the merge that were not part of either of the branches/trees being merged Discarding users' work and mis-merging are both bad outcomes, especially when done silently, so naturally this rule was stated sternly -- but, unfortunately totally ignored in practice unless and until actual bugs were found. But, fear not: the bugs from this were fixed in commit ee6566e8d70d ("[PATCH] Rewrite read-tree", 2005-09-05) through a rewrite of read-tree (again, commit 55f39cf7551b has a more detailed explanation of how this affected merge). And it was fixed again in commit 160252f81626 ("git-merge-ours: make sure our index matches HEAD", 2005-11-03) ...and it was fixed again in commit 3ec62ad9ffba ("merge-octopus: abort if index does not match HEAD", 2016-04-09) ...and again in commit 65170c07d466 ("merge-recursive: avoid incorporating uncommitted changes in a merge", 2017-12-21) ...and again in commit eddd1a411d93 ("merge-recursive: enforce rule that index matches head before merging", 2018-06-30) ...with multiple testcases added to the testsuite that could be enumerated in even more commits. Then, finally, in a patch in the same series as the last fix above, the documentation about this requirement was fixed in commit 55f39cf7551b ("merge: fix misleading pre-merge check documentation", 2018-06-30), and we all lived happily ever after... Unfortunately, "ever after" apparently denotes a limited time and it expired today. The merge-recursive rule to enforce that index matches head was at the beginning of merge_trees() and would only trigger when opt->call_depth was 0. Since merge_recursive() doesn't call merge_trees() until after returning from recursing, this meant that the check wasn't triggered by merge_recursive() until it had first finished all the intermediate merges to create virtual merge bases. That is a potentially HUGE amount of computation (and writing of intermediate merge results into the .git/objects directory) before it errors out and says, in effect, "Sorry, I can't do any merging because you have some local changes that would be overwritten." Trying to enforce that all of merge_trees(), merge_recursive(), and merge_recursive_generic() checked the index == head condition earlier resulted in a bunch of broken tests. It turns out that merge_recursive() has code to drop and reload the cache while recursing to create intermediate virtual merge bases, but unfortunately that code runs even when no recursion is necessary. This unconditional dropping and reloading of the cache masked a few bugs: * builtin/merge-recursive.c: didn't even bother loading the index. * builtin/stash.c: feels like a fake 'builtin' because it repeatedly invokes git subprocesses all over the place, mixed with other operations. In particular, invoking "git reset" will reset the index on disk, but the parent process that invoked it won't automatically have its in-memory index updated. * t3030-merge-recursive.h: this test has always been broken in that it didn't make sure to make index match head before running. But, it didn't care about the index or even the merge result, just the verbose output while running. While commit eddd1a411d93 ("merge-recursive: enforce rule that index matches head before merging", 2018-06-30) should have uncovered this broken test, it used a test_must_fail wrapper around the merge-recursive call because it was known that the merge resulted in a rename/rename conflict. Thus, that fix only made this test fail for a different reason, and since the index == head check didn't happen until after coming all the way back out of the recursion, the testcase had enough information to pass the one check that it did perform. So, load the index in builtin/merge-recursive.c, reload the in-memory index in builtin/stash.c, and modify the t3030 testcase to correctly setup the index and make sure that the test fails in the expected way (meaning it reports a rename/rename conflict). This makes sure that all callers actually make the index match head. The next commit will then enforce the condition that index matches head earlier so this problem doesn't return in the future. Signed-off-by: Elijah Newren --- builtin/merge-recursive.c | 4 ++++ builtin/stash.c | 2 ++ t/t3030-merge-recursive.sh | 9 ++++++++- 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/builtin/merge-recursive.c b/builtin/merge-recursive.c index 5b910e351e..a4bfd8fc51 100644 --- a/builtin/merge-recursive.c +++ b/builtin/merge-recursive.c @@ -1,3 +1,4 @@ +#include "cache.h" #include "builtin.h" #include "commit.h" #include "tag.h" @@ -63,6 +64,9 @@ int cmd_merge_recursive(int argc, const char **argv, const char *prefix) if (argc - i != 3) /* "--" "" "" */ die(_("not handling anything other than two heads merge.")); + if (repo_read_index_unmerged(the_repository)) + die_resolve_conflict("merge"); + o.branch1 = argv[++i]; o.branch2 = argv[++i]; diff --git a/builtin/stash.c b/builtin/stash.c index b5a301f24d..4aa47785f9 100644 --- a/builtin/stash.c +++ b/builtin/stash.c @@ -427,6 +427,8 @@ static int do_apply_stash(const char *prefix, struct stash_info *info, return error(_("could not save index tree")); reset_head(); + discard_cache(); + read_cache(); } } diff --git a/t/t3030-merge-recursive.sh b/t/t3030-merge-recursive.sh index ff641b348a..a37bcc58a0 100755 --- a/t/t3030-merge-recursive.sh +++ b/t/t3030-merge-recursive.sh @@ -667,15 +667,22 @@ test_expect_success 'merging with triple rename across D/F conflict' ' test_expect_success 'merge-recursive remembers the names of all base trees' ' git reset --hard HEAD && + # make the index match $c1 so that merge-recursive below does not + # fail early + git diff --binary HEAD $c1 -- | git apply --cached && + # more trees than static slots used by oid_to_hex() for commit in $c0 $c2 $c4 $c5 $c6 $c7 do git rev-parse "$commit^{tree}" done >trees && - # ignore the return code -- it only fails because the input is weird + # ignore the return code; it only fails because the input is weird... test_must_fail git -c merge.verbosity=5 merge-recursive $(cat trees) -- $c1 $c3 >out && + # ...but make sure it fails in the expected way + test_i18ngrep CONFLICT.*rename/rename out && + # merge-recursive prints in reverse order, but we do not care sort expect && sed -n "s/^virtual //p" out | sort >actual && -- 2.23.0.rc2.32.g2123e9e4e4