[RFC PATCH 15/35] update: fake a reverse order of parents in message

[Felipe Contreras <felipe.contreras@gmail.com>]

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
---
 builtin/merge.c   |  1 +
 fmt-merge-msg.c   | 21 +++++++++++++++++++--
 fmt-merge-msg.h   |  3 ++-
 t/t5563-update.sh | 10 +++++++++-
 4 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index b9c6c43d8f..cb476958ad 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1136,6 +1136,7 @@ static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *mer
 	opts.add_title = !have_message;
 	opts.shortlog_len = shortlog_len;
 	opts.credit_people = (0 < option_edit);
+	opts.reverse_parents = reverse_parents;
 
 	fmt_merge_msg(merge_names, merge_msg, &opts);
 	if (merge_msg->len)
diff --git a/fmt-merge-msg.c b/fmt-merge-msg.c
index 0f66818e0f..1f840711cc 100644
--- a/fmt-merge-msg.c
+++ b/fmt-merge-msg.c
@@ -432,6 +432,19 @@ static int dest_suppressed(const char *dest_branch)
 	return 0;
 }
 
+static void fmt_update_msg_title(struct strbuf *out, const char *current_branch)
+{
+	struct src_data *src_data;
+	strbuf_addf(out, "Merge branch '%s'", current_branch);
+	src_data = srcs.items[0].util;
+	if (src_data->branch.nr) {
+		const char *branch_name = src_data->branch.items[0].string;
+		if (!dest_suppressed(branch_name))
+			strbuf_addf(out, " into %s", branch_name);
+	}
+	strbuf_addch(out, '\n');
+}
+
 static void fmt_merge_msg_title(struct strbuf *out,
 				const char *current_branch)
 {
@@ -665,8 +678,12 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
 			die("error in line %d: %.*s", i, len, p);
 	}
 
-	if (opts->add_title && srcs.nr)
-		fmt_merge_msg_title(out, current_branch);
+	if (opts->add_title && srcs.nr) {
+		if (opts->reverse_parents)
+			fmt_update_msg_title(out, current_branch);
+		else
+			fmt_merge_msg_title(out, current_branch);
+	}
 
 	if (origins.nr)
 		fmt_merge_msg_sigs(out);
diff --git a/fmt-merge-msg.h b/fmt-merge-msg.h
index f2ab0e0085..fbdb1c905e 100644
--- a/fmt-merge-msg.h
+++ b/fmt-merge-msg.h
@@ -7,7 +7,8 @@
 
 struct fmt_merge_msg_opts {
 	unsigned add_title:1,
-		credit_people:1;
+		credit_people:1,
+		reverse_parents:1;
 	int shortlog_len;
 };
 
diff --git a/t/t5563-update.sh b/t/t5563-update.sh
index 72d6a357a1..aabbf5a965 100755
--- a/t/t5563-update.sh
+++ b/t/t5563-update.sh
@@ -7,6 +7,13 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+check_msg () {
+	test "$2" != "master" && into=" into '$2'"
+	echo "Merge branch '$1'${into}" > expected
+	git log -1 --format=%s > actual &&
+	test_cmp expected actual
+}
+
 test_expect_success 'setup' '
 	echo one > file &&
 	git add file &&
@@ -55,7 +62,8 @@ test_expect_success 'git update non-fast-forward with merge' '
 	git reset --hard master &&
 	git update --merge &&
 	test_cmp_rev @^2 master &&
-	test_cmp_rev @^1 other
+	test_cmp_rev @^1 other &&
+	check_msg test other
 	)
 '
 
-- 
2.32.0.36.g70aac2b1aa