Re: bug report: cover letter is inheriting last patch's message ID with send-email

From: Junio C Hamano <gitster@pobox.com>
Date: May 17, 2023, 20:04 UTC
Message-ID: <xmqqfs7upvvw.fsf@gitster.g>
In-Reply-To: <CAD=FV=XnzFrczC1dvsHYgNabZMhC7-K1uG8=MH20qNE25o0CEA@mail.gmail.com>

Doug Anderson <dianders@chromium.org> writes:

Show 5 quoted lines

> Yes. It exists in all of the patches except 0000-cover-letter.patch.
> ...but when the mail gets actually sent the cover letter and last
> patch (0006 in the case I reported) end up sharing the same Change ID.
> With older versions of git send-email the cover letter would get an
> auto-generated Message-Id.

Yeah, I think the patch I sent in the thread should help; I'd appreciate it if you folks can test and verify.

Show 14 quoted lines

>> I suspect that
>> is the root cause of the problem; if 000[1-6]-*.patch already has
>> their own Message-ID: because --thread is used when running
>> git-format-patch, they would also have In-Reply-To: and References:,
>> but there is no way for them to reference 0000-cover-letter.patch
>> (because format-patch did not get a chance to generate Message-ID to
>> it), is there?
>
> The patches were generated with git-format-patch but the Message-ID
> was added by patman [1]. The Message-ID encodes the local Change-Id
> which can make it easier to associate one version of the same patch
> with another (same reason gerrit uses Change-Id) [2]. There is no
> Change-Id associated with the cover letter so patman doesn't bother
> adding one there and has always just let it be auto-generated.

> We
> could certainly change patman to make up a Message-Id for the cover
> letter, but there is no real need.

This is a tangent, as I think the earlier patch should fix the regression, but wouldn't a recipient of such a series have a hard time to locate and group the patches in the same series with the cover letter, without having In-Reply-To: or References: that links the later message back to the initial message (i.e. cover letter)? Assigning a Message-ID to the cover, and referencing it from the patches via In-Reply-To:, is what is commonly done, I think, for that kind of threading.

Thanks.