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Sender: Junio C Hamano <jch2355@gmail.com>
From:   Junio C Hamano <gitster@pobox.com>
To:     Jeff King <peff@peff.net>
Cc:     "brian m. carlson" <sandals@crustytoothpaste.net>,
        Adam Majer <adamm@zombino.com>, git@vger.kernel.org
Subject: Re: git clone of empty repositories doesn't preserve hash
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Date:   Wed, 26 Apr 2023 08:42:17 -0700
In-Reply-To: <20230426105134.GA130148@coredump.intra.peff.net> (Jeff King's
        message of "Wed, 26 Apr 2023 06:51:34 -0400")
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Jeff King <peff@peff.net> writes:

> We could send a capabilities^{} line, which Git has supported on the
> client side since eb398797cd (connect: advertized capability is not a
> ref, 2016-09-09). So sending it should not break even old clients
> (though we would have to check what alternate implementations like
> libgit2 or dulwich do; we know JGit supports it).

Ah, I forgot all about that JGit workaround.  Yes, we can exploit
it, and any implementation that does not understand it correctly
(including git before 13e67aa3 (v0 protocol: fix sha1/sha256
confusion for capabilities^{}, 2023-04-14)) does not work with JGit
when cloning an empty repository anyway, so it is not all that bad.

But I tend to agree with your conclusion that it may be an update
for the sake of completeness to retrofit v0/v1 on the serving side.
It would not help any real-world use cases all that much.

Thanks.