xdelta multi-parent hack ?

[Aaron Bentley]

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Robert Collins wrote:
> On Fri, 2007-06-22 at 12:47 -0500, John Arbash Meinel wrote:
> I have another thought, which is that we could consider generating a
> single recipe to reconstruct a revision rather than the recursive
> recipes we're looking at today.
> 
> E.g. (using a single parent example) rather than:
> text1 + delta2 = text2
> text2 + delta3 = text3
> ...            = TextIRequested
> 
> If we assume everything is stored as deltas, then we can reconstruct a
> text by listing the delta elements that make it up:
> rev1 bytes 40-50
> rev2 bytes 20-70
> rev3 bytes 200-201

That's a very interesting thought.  I designed MultiParent Diff
specifically to avoid reconstructing intermediate versions.  But the
line lookup, even though it doesn't do recursive function calls, is
still a recursive algorithm.

You're essentially setting it up so that the build parents of each
revision are all of the ancestors whose lines it contains.  Basically
precalculated diff composition.

Aaron
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