Jeff King <p...@peff.net> writes:
> ... The reason we do not store thin-packs on disk is that you
> run into problems with cycles in the delta graph (e.g., A deltas against
> B, which deltas against C, which deltas against A; at one point you had
> a full copy of one object which let you create the cycle, but you later
> deleted it as redundant with the delta, and now you cannot reconstruct
> any of the objects).
As an extension to that is that a thin-pack will make the "validity"
of a single pack dependent on its surroundings, making "verify-pack"
useless. It may say "everything is fine", but corruption of another
pack that holds a base object a delta in it depends on will render
the pack unusable.
With the current arrangement, if you grab a single pack and re-idx
it, you know you can reconstruct all the objects in it.
The original reason was not cycles; it was primarily because we did
not want to have to map more than one packfile while reconstructing
the delta chain for a single object (this was way before the "open
small mmap windows into a large packfile" was invented).
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