From: Christian Couder <christian.couder@gmail.com>
Date: Mon, 30 Jun 2014 10:52:29 GMT
Subject: Re: [PATCH v3 1/4] replace: add --graft option
Message-ID: <CAP8UFD3w2s8tQ0OVe2eb9AmdsZhDeVJqNBUXewcbBxqs=id+HA@mail.gmail.com>
In-Reply-To: <xmqqr426zyw6.fsf@gitster.dls.corp.google.com>

On Mon, Jun 30, 2014 at 8:37 AM, Junio C Hamano <gitster@pobox.com> wrote:
> 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?

I think we are talking about the same thing but I might not have been clear.

> 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.

Ok, this is what is done right now by the patch series.

> 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.

Yeah, it might be a good idea to drop the "mergetag", but note that
anyway such a commit probably has a title like "Merge tag '<tag>'" and
we won't automatically change this title and this title will be wrong
(because we are not merging anymore this tag).

So anyway in this case, --graft will do something that is not good. So
it might be better in this case to just error out and say that it
would be better to use --edit instead of --graft.