Subject: Re: [PATCH 1/2] b4: introduce configuration for the Git project

From: Junio C Hamano <[email-masked]>
Date: Thu, 04 Jun 2026 10:11:37 +0900

SZEDER Gábor <[email-masked]> writes:

> No, in Git shallow threading means that all patches are sent as a
> respose to the current cover letter, period.  It has nothing to do
> with whether the current cover letter is sent as a reply to the cover
> letter of the first or the previous version.
> ...
> Deep threading means that every mail is a reply to the previous one.
> Again, it has nothing to do with the relation of the current cover
> letter and the previous cover letters.
>
> Therefore, we do not recommend deep threading.

The above exactly matches my understanding of the current best
practice.  Inside an iteration of a series, we want a cover letter
with everybody else responding to it.  We do not have a word to
describe how the latest iteration refers to its previous iteration
via In-reply-to: or References: headers, but our preference is to
make the cover letter of iteration N+1 to be a response to the cover
letter of iteration N.

For a single-patch topic (without a cover letter) with multiple
iterations, each iteration would be response to its previous
iteration, which may make it look like "deep threading", but as you
pointed out, the "deep threading" concept does not go across
iterations.

Having said that, I've seen a cover letter of iteration N (for any
value of N > 1) that respondes to the cover letter of the initial
iteration.  While it seems not to break "br" and the lore archive
does not seem unhappy about it, I am not sure if tooling used by
other people are also happy with it.

Thanks.