Re: [PATCH v2 1/2] pretty: add X-Change-ID to mail formats

From: Drew DeVault <drew@ddevault.org>
Date: Jul 6, 2025, 10:41 UTC
Message-ID: <DB4WQTRHWZN3.3VG20AZDK8VN@ddevault.org>
In-Reply-To: <PN3PR01MB9597069B8CF014BFE01B53F3B84CA@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>

On Sun Jul 6, 2025 at 8:20 AM CEST, Aditya Garg wrote:

Show 6 quoted lines

> I don't think we should add it to email headers. There are many email providers
> which do not allow custom headers in the emails. For example if you are using
> protonmail bridge or any third party protonmail client, the headers are not
> preserved. Similarly, if you are using MS Graph to send emails, headers are
> again not preserved. We should also consider cases when people use Thunderbird,
> Mutt or something similar to send emails, rather than git send-email.

As far as I can tell, this isn't actually true. I looked into it and protonmail and MS Graph both seem to support custom headers. I have also verified that mutt will preserve the header when you edit the email normally with mutt -H. If you're sending an email with Thunderbird, none of these things are preserved (including From, Subject, etc), and the best you can hope for is attaching the patch, in which case X-Change-ID will be preserved unmolested.

Moreover, if the change-id header is lost, it's not the end of the world, it just degrades to the present-day state of affairs, in which you cannot use it to associate patches with prior versions.

> The headers IMO should include the standard ones like From, Subject etc.
> Custom headers should be a part of body, just like we do Signed-off-by, Link etc.

Trailers and headers are different. The main point of the change-id discussion earlier on this list was to avoid adding trailers.

I also suspect that if we added this as an "inbody header" that older git implementations would ingest the X-Change-ID header into the commit message, which is not a desirable behavior.

IMO the right way forward is to use a mail header.