Merge branch 'en/remerge-diff-fixes'

Fix a few "git log --remerge-diff" bugs.

* en/remerge-diff-fixes:
  diff: fix filtering of merge commits under --remerge-diff
  diff: fix filtering of additional headers under --remerge-diff
  diff: have submodule_format logic avoid additional diff headers

diff.c

@@ -3399,6 +3399,21 @@ static void add_formatted_headers(struct strbuf *msg,
 				     line_prefix, meta, reset);
 }
 
+static int diff_filepair_is_phoney(struct diff_filespec *one,
+				   struct diff_filespec *two)
+{
+	/*
+	 * This function specifically looks for pairs injected by
+	 * create_filepairs_for_header_only_notifications().  Such
+	 * pairs are "phoney" in that they do not represent any
+	 * content or even mode difference, but were inserted because
+	 * diff_queued_diff previously had no pair associated with
+	 * that path but we needed some pair to avoid losing the
+	 * "remerge CONFLICT" header associated with the path.
+	 */
+	return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
+}
+
 static void builtin_diff(const char *name_a,
 			 const char *name_b,
 			 struct diff_filespec *one,
@@ -3430,14 +3445,16 @@ 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)) &&
+	    (!diff_filepair_is_phoney(one, two))) {
 		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)) &&
+		   (!diff_filepair_is_phoney(one, two))) {
 		show_submodule_inline_diff(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
@@ -3457,12 +3474,12 @@ static void builtin_diff(const char *name_a,
 	b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
 	lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
 	lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
-	if (!DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two)) {
+	if (diff_filepair_is_phoney(one, two)) {
 		/*
-		 * We should only reach this point for pairs from
+		 * We should only reach this point for pairs generated from
 		 * create_filepairs_for_header_only_notifications().  For
-		 * these, we should avoid the "/dev/null" special casing
+		 * these, we want to avoid the "/dev/null" special casing
-		 * above, meaning we avoid showing such pairs as either
+		 * above, because we do not want such pairs shown as either
 		 * "new file" or "deleted file" below.
 		 */
 		lbl[0] = a_one;
@@ -5853,6 +5870,7 @@ static void diff_flush_patch(struct diff_filepair *p, struct diff_options *o)
 {
 	int include_conflict_headers =
 	    (additional_headers(o, p->one->path) &&
+	     !o->pickaxe_opts &&
 	     (!o->filter || filter_bit_tst(DIFF_STATUS_UNMERGED, o)));
 
 	/*
@@ -5908,6 +5926,8 @@ int diff_queue_is_empty(struct diff_options *o)
 	int i;
 	int include_conflict_headers =
 	    (o->additional_path_headers &&
+	     strmap_get_size(o->additional_path_headers) &&
+	     !o->pickaxe_opts &&
 	     (!o->filter || filter_bit_tst(DIFF_STATUS_UNMERGED, o)));
 
 	if (include_conflict_headers)

t/t4069-remerge-diff.sh

@@ -2,7 +2,6 @@
 
 test_description='remerge-diff handling'
 
-TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 # This test is ort-specific
@@ -57,6 +56,11 @@ test_expect_success 'remerge-diff on a clean merge' '
 	test_cmp expect actual
 '
 
+test_expect_success 'remerge-diff on a clean merge with a filter' '
+	git show --oneline --remerge-diff --diff-filter=U bc_resolution >actual &&
+	test_must_be_empty actual
+'
+
 test_expect_success 'remerge-diff with both a resolved conflict and an unrelated change' '
 	git log -1 --oneline ab_resolution >tmp &&
 	cat <<-EOF >>tmp &&
@@ -90,6 +94,22 @@ test_expect_success 'remerge-diff with both a resolved conflict and an unrelated
 	test_cmp expect actual
 '
 
+test_expect_success 'pickaxe still includes additional headers for relevant changes' '
+	# reuses "expect" from the previous testcase
+
+	git log --oneline --remerge-diff -Sacht ab_resolution >tmp &&
+	sed -e "s/[0-9a-f]\{7,\}/HASH/g" tmp >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'can filter out additional headers with pickaxe' '
+	git show --remerge-diff --submodule=log --find-object=HEAD ab_resolution >actual &&
+	test_must_be_empty actual &&
+
+	git show --remerge-diff -S"not present" --all >actual &&
+	test_must_be_empty actual
+'
+
 test_expect_success 'setup non-content conflicts' '
 	git switch --orphan base &&
 
@@ -185,6 +205,14 @@ 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 &&