[rb-general] rb-prefix-map spec: don't be as democratic to consumers

[Ximin Luo]

Ximin Luo:
> [..]
> 
> In other words, find values for:
> 
> - some fixed target directories tlist = [t0 .. tn]
> - source directoies alist = [A0 .. An]
> - path Ap a child of Ai for some i
> - source directoies blist = [B0 .. Bn]
> - path Bp a child of Bi for some i

Actually in a real world situation with a non-buggy producer this constraint is too loose, it would instead be:

- path Ap = Ai "/" Rp for some i
- path Bp = Bi "/" Rp for the same i (and the same Rp)

> 
> such that:
> 
> (
> algorithm (1) applying (zip alist tlist) to path Ap
> equals
> algorithm (1) applying (zip blist tlist) to path Bp
> 
> AND
> 
> algorithm (2) applying (zip alist tlist) to path Ap
> does not equal
> algorithm (2) applying (zip blist tlist) to path Bp
> )
> 
> OR
> 
> (as in the above parens but with "equals" and "does not equal" swapped around)
> 
> My intuition is that no such values exist. I don't particularly want to spend time doing a proof of this but I can if you insist.
> 

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