[PATCH RFC 1/2] builtin/history: abort reword on unchanged message

From

Pablo Sabater <pabloosabaterr@gmail.com>

Date

Jun 7, 2026, 20:07 UTC

Message-ID

<20260607-ps-history-reword-v1-1-ba43a3cbb81b@gmail.com>

In-Reply-To

<20260607-ps-history-reword-v1-0-ba43a3cbb81b@gmail.com>

`git commit --amend` and `git rebase -i` + reword share this behavior,
however `git history reword` is different:
1. Works in-memory without touching the index or the worktree [1], so
   there are no side effects like staged files that could justify
   rewriting the history when the commit message is the same.
2. `git history` by default updates all the branches [2] that contain the
   original commit making it more costly than `git rebase -i` that only
   updates the current branch.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 builtin/history.c         | 10 ++++++++++
 t/t3451-history-reword.sh | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/builtin/history.c b/builtin/history.c
index 0fc06fb204..51a22a9a1c 100644
--- a/builtin/history.c
+++ b/builtin/history.c
@@ -135,6 +135,13 @@ static int commit_tree_ext(struct repository *repo,
 					  original_body, action, &commit_message);
 		if (ret < 0)
 			goto out;
+
+		if (!strcmp(original_body, commit_message.buf)) {
+			fprintf(stderr, _("Message unchanged,"
+					  " aborting reword.\n"));
+			ret = 1;
+			goto out;
+		}
 	} else {
 		strbuf_addstr(&commit_message, original_body);
 	}
@@ -718,6 +725,9 @@ static int cmd_history_reword(int argc,
 	if (ret < 0) {
 		ret = error(_("failed writing reworded commit"));
 		goto out;
+	} else if (ret == 1) {
+		ret = 0;
+		goto out;
 	}
 
 	strbuf_addf(&reflog_msg, "reword: updating %s", argv[0]);
diff --git a/t/t3451-history-reword.sh b/t/t3451-history-reword.sh
index de7b357685..54ea8a7207 100755
--- a/t/t3451-history-reword.sh
+++ b/t/t3451-history-reword.sh
@@ -396,4 +396,24 @@ test_expect_success 'retains changes in the worktree and index' '
 	)
 '
 
+test_expect_success 'aborts if the commit message is the same' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit first &&
+		test_commit second &&
+
+		git rev-parse HEAD >oid-before &&
+		write_script fake-editor.sh <<-\EOF &&
+		true
+		EOF
+		test_set_editor "$(pwd)"/fake-editor.sh &&
+		git history reword HEAD 2>err &&
+		git rev-parse HEAD >oid-after &&
+		test_cmp oid-before oid-after &&
+		test_grep "Message unchanged" err
+	)
+'
+
 test_done

-- 
2.54.0