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From: Junio C Hamano <gitster@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-gpio\@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        Git Mailing List <git@vger.kernel.org>
Subject: Re: [GIT PULL] GPIO bulk changes for kernel v4.6
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	<56EB9B0C.4050507@nvidia.com>
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Date: Fri, 18 Mar 2016 09:37:31 -0700
In-Reply-To: <CA+55aFwbRVG-5AW+NnMOFZ_hU5i+i7f3FxgEt9Qm7B6pEd7x0g@mail.gmail.com>
	(Linus Torvalds's message of "Fri, 18 Mar 2016 08:47:02 -0700")
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Linus Torvalds <torvalds@linux-foundation.org> writes:

> It's literally just the fact that "git merge" does it with no extra
> flags or checks. I'd like people to have to be aware of what they are
> doing when they merge two different projects, not do it by mistake.
>
> So making it conditional on a flag like "--no-common-root" is what I'd look for.

I think I said essentially the same thing in a separate message; I
am not sure "--no-common-root" is a good name, but I think it is
better to be more explicit than tying this to a strategy.

> I don't think the original "resolve" did it, for example. You can't do
> a three-way merge without a base.

Yes, and that continues to this day:

        # Give up if we are given two or more remotes -- not handling octopus.
        case "$remotes" in
        ?*' '?*)
                exit 2 ;;
        esac

        # Give up if this is a baseless merge.
        if test '' = "$bases"
        then
                exit 2
        fi

This is a tangent but I wonder if we should say why we refuse to
the standard error before calling these two "exit"s.