From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [PATCH 0/4] Speed up git tag --contains
Date: Wed, 6 Jul 2011 01:56:23 -0500
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To: Jeff King <peff@peff.net>
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Jeff King wrote:

> The problem is that existing objects don't have this generation number.
> It's easy to calculate, though, and we could in theory use a notes-cache
> to store it externally. Obviously the complexity and performance aren't
> going to be as good as if it were just in the commit object, but we're
> sadly 6 years too late to make that decision.

I am still digesting the rest of what you wrote, but wouldn't this be
easy to do today?  One could just use a notes-cache while prototyping
and if it seems to work well, introduce new loose and packed object
formats that include a field for the cached generation number.