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From: "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Victoria Dye <vdye@github.com>, Derrick Stolee <stolee@gmail.com>,
	Lessley Dennington <lessleydennington@gmail.com>,
	Elijah Newren <newren@gmail.com>,
	Elijah Newren <newren@gmail.com>
Subject: [PATCH 2/5] unpack-trees: fix accidental loss of user changes
Date: Thu, 13 Jan 2022 16:43:47 +0000	[thread overview]
Message-ID: <1e3958576e2a132180f8c5d20acc1315d3062119.1642092230.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1114.git.1642092230.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

For sparse-checkouts, we don't want unpack-trees to error out on files
that are missing from the worktree, so there has traditionally been
logic to make it skip the verify_uptodate() check for these.
Unfortunately, it was skipping the verify_uptodate() check for files
that were expected to *become* SKIP_WORKTREE.  For files that were not
already SKIP_WORKTREE, that can cause us to later delete the file in
apply_sparse_checkout().  Only skip the check for files that were
already SKIP_WORKTREE as well to avoid lightly discarding important
changes users may have made to files.

Note 1: unpack-trees.c is already a bit complex, and the logic around
CE_SKIP_WORKTREE and CE_NEW_SKIP_WORKTREE in that file are no exception.
I also tried just replacing CE_NEW_SKIP_WORKTREE with CE_SKIP_WORKTREE
in the verify_uptodate() check instead of checking for both flags, and
found that it also fixed this bug and passed all the tests.  I also
attempted to devise a few testcases that might trip either variant of my
fix and was unable to find any problems.  It may be that just checking
CE_SKIP_WORKTREE is a better fix, but I'm not sure.  I thought it
was a bit safer to strictly reduce the number of cases where we skip the
up-to-date check rather than just toggling which kind of cases skip it,
and thus went with the current variant of the fix.

Note 2: I also wondered if verify_absent() might have a similar bug, but
despite my attempts to try to devise a testcase that would trigger such
a thing, I couldn't find any problematic testcases.  Thus, this patch
makes no attempt to apply similar changes to verify_absent() and
verify_absent_if_directory().

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 t/t1011-read-tree-sparse-checkout.sh | 2 +-
 unpack-trees.c                       | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/t/t1011-read-tree-sparse-checkout.sh b/t/t1011-read-tree-sparse-checkout.sh
index 1b2395b8a82..4ed0885bf2f 100755
--- a/t/t1011-read-tree-sparse-checkout.sh
+++ b/t/t1011-read-tree-sparse-checkout.sh
@@ -197,7 +197,7 @@ test_expect_success 'read-tree will not throw away dirty changes, non-sparse' '
 	grep -q dirty init.t
 '
 
-test_expect_failure 'read-tree will not throw away dirty changes, sparse' '
+test_expect_success 'read-tree will not throw away dirty changes, sparse' '
 	echo "/*" >.git/info/sparse-checkout &&
 	read_tree_u_must_succeed -m -u HEAD &&
 
diff --git a/unpack-trees.c b/unpack-trees.c
index 98e2f2e0e6f..6d9d89c662a 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -2059,7 +2059,9 @@ static int verify_uptodate_1(const struct cache_entry *ce,
 int verify_uptodate(const struct cache_entry *ce,
 		    struct unpack_trees_options *o)
 {
-	if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
+	if (!o->skip_sparse_checkout &&
+	    (ce->ce_flags & CE_SKIP_WORKTREE) &&
+	    (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
 		return 0;
 	return verify_uptodate_1(ce, o, ERROR_NOT_UPTODATE_FILE);
 }
-- 
gitgitgadget


  parent reply	other threads:[~2022-01-13 16:44 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-13 16:43 [PATCH 0/5] Remove the present-despite-SKIP_WORKTREE class of bugs (for sparse-checkouts) Elijah Newren via GitGitGadget
2022-01-13 16:43 ` [PATCH 1/5] t1011: add testcase demonstrating accidental loss of user modifications Elijah Newren via GitGitGadget
2022-01-13 16:43 ` Elijah Newren via GitGitGadget [this message]
2022-01-13 16:43 ` [PATCH 3/5] repo_read_index: clear SKIP_WORKTREE bit from files present in worktree Elijah Newren via GitGitGadget
2022-01-13 16:43 ` [PATCH 4/5] Update documentation related to sparsity and the skip-worktree bit Elijah Newren via GitGitGadget
2022-01-13 16:43 ` [PATCH 5/5] Accelerate clear_skip_worktree_from_present_files() by caching Elijah Newren via GitGitGadget
2022-01-13 23:35   ` Elijah Newren
2022-01-14 15:59 ` [PATCH v2 0/5] Remove the present-despite-SKIP_WORKTREE class of bugs (for sparse-checkouts) Elijah Newren via GitGitGadget
2022-01-14 15:59   ` [PATCH v2 1/5] t1011: add testcase demonstrating accidental loss of user modifications Elijah Newren via GitGitGadget
2022-02-16  8:51     ` Ævar Arnfjörð Bjarmason
2022-02-16 16:02       ` Elijah Newren
2022-01-14 15:59   ` [PATCH v2 2/5] unpack-trees: fix accidental loss of user changes Elijah Newren via GitGitGadget
2022-01-14 15:59   ` [PATCH v2 3/5] repo_read_index: clear SKIP_WORKTREE bit from files present in worktree Elijah Newren via GitGitGadget
2022-02-16  8:57     ` Ævar Arnfjörð Bjarmason
2022-02-16 16:08       ` Elijah Newren
2022-02-19  1:06     ` Jonathan Nieder
2022-02-19 16:42       ` Elijah Newren
2022-02-19 18:14         ` Jonathan Nieder
2022-02-20  5:28           ` Elijah Newren
2022-02-20 16:56       ` Derrick Stolee
2022-02-22 23:17         ` Jonathan Nieder
2022-01-14 15:59   ` [PATCH v2 4/5] Update documentation related to sparsity and the skip-worktree bit Elijah Newren via GitGitGadget
2022-02-16  9:15     ` Ævar Arnfjörð Bjarmason
2022-02-16 16:21       ` Elijah Newren
2022-01-14 15:59   ` [PATCH v2 5/5] Accelerate clear_skip_worktree_from_present_files() by caching Elijah Newren via GitGitGadget
2022-01-15  1:39     ` Victoria Dye
2022-02-16  9:32     ` Ævar Arnfjörð Bjarmason
2022-02-16 16:30       ` Elijah Newren
2022-02-17  4:40         ` Elijah Newren
2022-01-15  1:51   ` [PATCH v2 0/5] Remove the present-despite-SKIP_WORKTREE class of bugs (for sparse-checkouts) Victoria Dye

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