[PATCH 1/3] diff: have submodule_format logic avoid additional diff headers

From: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 31, 2022, 06:21 UTC
Message-ID: <e4414cf630da284bdb11f5613ca0ce6413c6a443.1661926908.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1342.git.1661926908.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

Commit 95433eeed9 ("diff: add ability to insert additional headers for paths", 2022-02-02) introduced the possibility of additional headers, created in create_filepairs_for_header_only_notifications(). These are represented by inserting additional pairs in diff_queued_diff which always have a mode of 0 and a null_oid. When these were added, one code path was noted to assume that at least one of the diff_filespecs in the pair were valid, and that codepath was corrected.

The submodule_format handling is another codepath with the same issue; it would operate on these additional headers and attempt to display them as submodule changes. Prevent that by explicitly checking for both modes being 0.

Reported-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
---
 diff.c                  | 6 ++++--
 t/t4069-remerge-diff.sh | 8 ++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/diff.c b/diff.c
index 974626a6211..be23f660570 100644
--- a/diff.c
+++ b/diff.c
@@ -3429,14 +3429,16 @@ static void builtin_diff(const char *name_a,
 
 	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
 	    (!one->mode || S_ISGITLINK(one->mode)) &&
-	    (!two->mode || S_ISGITLINK(two->mode))) {
+	    (!two->mode || S_ISGITLINK(two->mode)) &&
+	    (one->mode || two->mode)) {
 		show_submodule_diff_summary(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
 		return;
 	} else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
 		   (!one->mode || S_ISGITLINK(one->mode)) &&
-		   (!two->mode || S_ISGITLINK(two->mode))) {
+		   (!two->mode || S_ISGITLINK(two->mode)) &&
+		   (one->mode || two->mode)) {
 		show_submodule_inline_diff(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
diff --git a/t/t4069-remerge-diff.sh b/t/t4069-remerge-diff.sh
index 9e7cac68b1c..e3e6fbd97b2 100755
--- a/t/t4069-remerge-diff.sh
+++ b/t/t4069-remerge-diff.sh
@@ -185,6 +185,14 @@ test_expect_success 'remerge-diff w/ diff-filter=U: all conflict headers, no dif
 	test_cmp expect actual
 '
 
+test_expect_success 'submodule formatting ignores additional headers' '
+	# Reuses "expect" from last testcase
+
+	git show --oneline --remerge-diff --diff-filter=U --submodule=log >tmp &&
+	sed -e "s/[0-9a-f]\{7,\}/HASH/g" tmp >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'remerge-diff w/ diff-filter=R: relevant file + conflict header' '
 	git log -1 --oneline resolution >tmp &&
 	cat <<-EOF >>tmp &&

-- 
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