[PATCH v3 6/9] t4058: explore duplicate tree entry handling in a bit more detail

From: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date: Dec 29, 2020, 20:05 UTC
Message-ID: <8db27892c598a3976c0742e23563f1d360b8dee1.1609272328.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.929.v3.git.git.1609272328.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

While creating the last commit, I found a number of other cases where git would segfault when faced with trees that have duplicate entries. None of these segfaults are in the diffcore-rename code (they all occur in cache-tree and unpack-trees). Further, to my knowledge, no one has ever been adversely affected by these bugs, and given that it has been 15 years and folks have fixed a few other issues with historical duplicate entries (as noted in the last commit), I am not sure we will ever run into anyone having problems with these. So I am not sure these are worth fixing, but it doesn't hurt to at least document these failures in the same test file that is concerned with duplicate tree entries.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 t/t4058-diff-duplicates.sh | 67 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/t/t4058-diff-duplicates.sh b/t/t4058-diff-duplicates.sh
index bd685089561..ad3f37d388d 100755
--- a/t/t4058-diff-duplicates.sh
+++ b/t/t4058-diff-duplicates.sh
@@ -119,4 +119,71 @@ test_expect_success 'diff-tree FROM duplicate tree, with renames' '
 	test_cmp expect actual
 '
 
+test_expect_success 'create a few commits' '
+	git commit-tree -m "Duplicate Entries" two^{tree} >commit_id &&
+	git branch base $(cat commit_id) &&
+
+	git commit-tree -p $(cat commit_id) -m "Just one" three^{tree} >up &&
+	git branch update $(cat up) &&
+
+	git commit-tree -p $(cat up) -m "Back to weird" two^{tree} >final &&
+	git branch final $(cat final) &&
+
+	rm commit_id up final
+'
+
+test_expect_failure 'git read-tree does not segfault' '
+	test_when_finished rm .git/index.lock &&
+	test_might_fail git read-tree --reset base
+'
+
+test_expect_failure 'reset --hard does not segfault' '
+	test_when_finished rm .git/index.lock &&
+	git checkout base &&
+	test_might_fail git reset --hard
+'
+
+test_expect_failure 'git diff HEAD does not segfault' '
+	git checkout base &&
+	GIT_TEST_CHECK_CACHE_TREE=false &&
+	git reset --hard &&
+	test_might_fail git diff HEAD
+'
+
+test_expect_failure 'can switch to another branch when status is empty' '
+	git clean -ffdqx &&
+	git status --porcelain -uno >actual &&
+	test_must_be_empty actual &&
+	git checkout update
+'
+
+test_expect_success 'forcibly switch to another branch, verify status empty' '
+	git checkout -f update &&
+	git status --porcelain -uno >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_success 'fast-forward from non-duplicate entries to duplicate' '
+	git merge final
+'
+
+test_expect_failure 'clean status, switch branches, status still clean' '
+	git status --porcelain -uno >actual &&
+	test_must_be_empty actual &&
+	git checkout base &&
+	git status --porcelain -uno >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_success 'switch to base branch and force status to be clean' '
+	git checkout base &&
+	GIT_TEST_CHECK_CACHE_TREE=false git reset --hard &&
+	git status --porcelain -uno >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_failure 'fast-forward from duplicate entries to non-duplicate' '
+	git merge update
+'
+
 test_done

-- 
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