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From:   Stefan Beller <sbeller@google.com>
Date:   Mon, 18 Sep 2017 13:06:59 -0700
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Subject: Re: [PATCH 2/8] protocol: introduce protocol extention mechanisms
To:     Brandon Williams <bmwill@google.com>
Cc:     "git@vger.kernel.org" <git@vger.kernel.org>,
        Jeff King <peff@peff.net>, Junio C Hamano <gitster@pobox.com>,
        Jonathan Nieder <jrnieder@gmail.com>,
        Bryan Turner <bturner@atlassian.com>,
        Jeff Hostetler <git@jeffhostetler.com>,
        Jonathan Tan <jonathantanmy@google.com>
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>> instead compared to the proposed configuration above.
>> (Even better yet, then people could play around with "v1 only"
>> and see how it falls apart on old servers)
>
> Except we can't start with an explicit whitelist because we must
> fallback to v0 if v1 isn't supported otherwise we would break people.
>
> That is unless we have the semantics of: If not configured v0 will be
> used, otherwise only use the configured protocol versions.
>

Good point.

Thinking about this, how about:

  If not configured, we do as we want. (i.e. Git has full control over
  it's decision making process, which for now is "favor v0 over v1 as
  we are experimenting with v1". This strategy may change in the future
  to "prefer highest version number that both client and server can speak".)

  If it is configured, "use highest configured number from the given set".

?