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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 13 Feb 2018 09:33:02 -0800
Message-ID: <CA+55aFxkYTeY9h=VHFXi=gbXsnsHCRMAVZ9=1_EsFGSqr0sj9g@mail.gmail.com>
Subject: Re: linux-next: unnecessary merge in the v4l-dvb tree
To:     Junio C Hamano <gitster@pobox.com>
Cc:     Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Git Mailing List <git@vger.kernel.org>
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On Tue, Feb 13, 2018 at 9:18 AM, Junio C Hamano <gitster@pobox.com> wrote:
>
> That makes me wonder if another heuristic I floated earlier is more
> appropriate.  When merging a tag object T, if refs/tags/T exists and
> it is that tag object, then an updated "merge" would default to "--ff";
> otherwise, it would keep the current default of creating a merge even
> when we could fast-forward, in order to record that tag T in the
> resulting history.

Oooh. Yes, that sounds like the right thing to do.

So the "no fast-forward" logic would trigger only if the name we used
for merging is one of the temporary ones (ie .git/{FETCH,MERGE}_HEAD),
not if the mentioned tag is already a normal tag reference.

Then it's very explicitly about "don't lose the signing information".

I'd still have to teach people to use "--only-ff" if they don't do the
"fetch and merge" model but literally just do  "git pull upstream
vX.Y", but at least the case Mauro describes would automatically just
DTRT.

Me likey.

           Linus