Subject: Re: RFC: Separate commit identification from Merkle hashing

From: "Eric S. Raymond" <[email-masked]>
Date: Mon, 20 May 2019 23:31:53 -0400

Jonathan Nieder <[email-masked]>:
> > I think it's a weakness, though, that most of it is written as though it
> > assumes only one hash transition will be necessary.  (This is me thinking
> > on long timescales again.)
> 
> Hm, can you point to what part of the doc suggested that?  Best to make
> the text clearer, to avoid confusing the next person.

I will reread it with an editorial eye and try to come up with
concrete suggestions, perhaps a patch. My relative ignorance
should actually be helpful here.

> >                                    The same technique (probably the
> > same code!) could be used to map the otherwise uninterpreted
> > commit-IDs I'm proposing to lookup keys.
> 
> No, since Git relies on commit IDs for integrity checking.  The hash
> function transition described in that document relies on
> round-tripping ability for the duration of the transition.

I do not quite understand this comment yet. But I don't think it
matters that I don't, and I will by the time I write any code.  I
expect the worst case is that the separated IDs require a different
lookup table from the hashes, but will resolve at the same speed.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>