Re: [PATCH v3 1/4] replace: add --graft option

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 30, 2014, 06:37 UTC
Message-ID: <xmqqr426zyw6.fsf@gitster.dls.corp.google.com>
In-Reply-To: <CAP8UFD25k4X0vVUDDTOj_XDqmShz-aHXFLKD5bruUYYLX6awow@mail.gmail.com>

Christian Couder <christian.couder@gmail.com> writes:

> Now, after having read the recent thread about "git verify-commit", I understand
> that you also want me to drop the signature of a tag that was merged, because
> such signatures are added to the commit message.

Huh? I am not sure if I follow. Perhaps we are talking about different things?

When you are preparing a replacement for an existing commit that merges a signed tag, there are two cases:

 - The replacement commit still merges the same signed tag; or

 - The replacement commit does not merge that signed tag (it may
   become a single-parent commit, or it may stay to be a merge but
   merges a different commit on the side branch).

In the former, it would be sensible to keep the "mergetag" and propagate it to the replacement; it is a signature over the tip of the side branch being merged by the original (and the replacement) merge, and the replacement will not affect the validity of the signature at all. In the latter, we do want to drop the "mergetag" for the parent you are losing in the replacement, because by definition it will be irrelevant.