From: Ben Knoble <ben.knoble@gmail.com>
Date: Mon, 08 Jun 2026 16:37:47 GMT
Subject: Re: [PATCH RFC 1/2] builtin/history: abort reword on unchanged message
Message-ID: <9A2F74F1-66D0-4015-B387-35B107ED6F7A@gmail.com>
In-Reply-To: <20260607-ps-history-reword-v1-1-ba43a3cbb81b@gmail.com>

I don’t have any strong opinions on the rest…

> Le 7 juin 2026 à 16:08, Pablo Sabater <pabloosabaterr@gmail.com> a écrit :
> 
> When using `git history reword` if the new message is the same as the
> original it continues anyway creating a new commit with the same
> message and updates its descendants, modifying the history after this
> 'reworded' commit even though there was no actual change.
> 
> `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.
> 
> Add a check if the original commit message is the same as the new one
> and abort if so.
> 
> [1]: https://lore.kernel.org/git/20260113-b4-pks-history-builtin-v11-8-e74ebfa2652d@pks.im/
> [2]: https://git-scm.com/docs/git-history#_description
> 
> 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
> +    )

…but I think this test case could do something like "GIT_EDITOR=true git history reword HEAD" and avoid the script?

> +'
> +
> test_done
> 
> --
> 2.54.0

Best,
Ben