From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from cloud.peff.net (cloud.peff.net [104.130.231.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BEE0A1862 for ; Sat, 25 May 2024 03:15:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=104.130.231.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716606919; cv=none; b=S/KVumPNmovLyDV+C0wHxEkU7Eow7tTStTSP8I8ctnfPHPCzjKchIj71v2S0vl+dt1PYTUYeKUHyKLIfq2mftbOnLdyzicWX7M5WRhM9nrQiiNHSNoPzMxsjrq71wAg30DFVirGfeS4nJDbICSvl0qTlVQPGCNdNiPTB1ak38fA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716606919; c=relaxed/simple; bh=tG5LIbi+fKqUcfJ5pvMJYlmYa789Ji6TRk8iN9M3ZIY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Rhdb0DzzaoWQEj+xaPNK6ZHaUacaZFdA5CRHQW1MpDuCZj3rmvztzDPCz8LtbgdtFxoYUj8CHnL3EIOuBI93RONMQCA0Lfo52c/mCoGjSmCQ/kOzcAU8P8W3mW5vyBuI2WbklpHGbpYjfzWo0uKWn9Zprh+Ppwzg1oALsL9bb30= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=peff.net; spf=pass smtp.mailfrom=peff.net; arc=none smtp.client-ip=104.130.231.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=peff.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=peff.net Received: (qmail 3819 invoked by uid 109); 25 May 2024 03:15:17 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with ESMTP; Sat, 25 May 2024 03:15:17 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 15314 invoked by uid 111); 25 May 2024 03:15:20 -0000 Received: from coredump.intra.peff.net (HELO coredump.intra.peff.net) (10.0.0.2) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Fri, 24 May 2024 23:15:20 -0400 Authentication-Results: peff.net; auth=none Date: Fri, 24 May 2024 23:15:16 -0400 From: Jeff King To: Taylor Blau Cc: git@vger.kernel.org, Elijah Newren , Patrick Steinhardt , Junio C Hamano Subject: Re: [PATCH v3 00/30] pack-bitmap: pseudo-merge reachability bitmaps Message-ID: <20240525031516.GB1889620@coredump.intra.peff.net> References: <20240523110532.GA1326297@coredump.intra.peff.net> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Thu, May 23, 2024 at 04:04:15PM -0400, Taylor Blau wrote: > On Thu, May 23, 2024 at 07:05:32AM -0400, Jeff King wrote: > > I wonder if the start of the pseudo-merge section should have a 4-byte > > version/flags field itself? I don't think that's something we've done > > before, and maybe it's overkill. I dunno. It's just a lot easier to do > > now than later. > > I think the tricky thing here would be that the extension itself is a > variable size, so every version would have to put the "extension size" > field in the same place. > > Otherwise, an older Git client which doesn't understand a future version > of the pseudo-merge extension wouldn't know how large the extension is, > and wouldn't be able to adjust the index_end field appropriately to skip > over it. > > Of course, we could make it a convention that says "all versions have to > place the extension size field at the same relative offset", but it > feels weird to read some of the extension while not understanding the > whole thing. Ah, yeah, I didn't think of that. That definitely complicates things. It certainly would be possible to have a version+size header at the start. Which is...basically reinventing the chunk format. Let's not worry about it for now, and as a long-term thing we might consider moving the bitmap format over to the chunk style. -Peff