From: Derrick Stolee <redacted>

While dogfooding, Johannes found a bug in the fetch.writeCommitGraph
config behavior. His example initially happened during a clone with
--recurse-submodules, we found that this happens with the first fetch
after cloning a repository that contains a submodule:

	$ git clone <url> test
	$ cd test
	$ git -c fetch.writeCommitGraph=true fetch origin
	Computing commit graph generation numbers: 100% (12/12), done.
	BUG: commit-graph.c:886: missing parent <hash1> for commit <hash2>
	Aborted (core dumped)

In the repo I had cloned, there were really 60 commits to scan, but
only 12 were in the list to write when calling
compute_generation_numbers(). A commit in the list expects to see a
parent, but that parent is not in the list.

A follow-up will fix the bug, but first we create a test that
demonstrates the problem.

I used "test_expect_failure" for the entire test instead of
"test_must_fail" only on the command that I expect to fail. This is
because the BUG() returns an exit code so test_must_fail complains.

Helped-by: Jeff King [off-list ref]
Helped-by: Johannes Schindelin [off-list ref]
Helped-by: Szeder Gábor [off-list ref]
Signed-off-by: Derrick Stolee <redacted>
---
 t/t5510-fetch.sh | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index ecabbe1616..e8ae3af0b6 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh

@@ -583,6 +583,23 @@ test_expect_success 'fetch.writeCommitGraph' '
 	)
 '
 
+test_expect_failure 'fetch.writeCommitGraph with submodules' '
+	pwd="$(pwd)" &&
+	git clone dups super &&
+	(
+		cd super &&
+		git submodule add "file://$pwd/three" &&
+		git commit -m "add submodule"
+	) &&
+	git clone "super" writeError &&
+	(
+		cd writeError &&
+		test_path_is_missing .git/objects/info/commit-graphs/commit-graph-chain &&
+		git -c fetch.writeCommitGraph=true fetch origin &&
+		test_path_is_file .git/objects/info/commit-graphs/commit-graph-chain
+	)
+'
+
 # configured prune tests
 
 set_config_tristate () {

-- 
gitgitgadget