Add dirstate.pathto and localrepo.pathto. Every time util.pathto is called, we have to pass the repo root and the repo cwd. dirstate.pathto is a simple convenience function that knows about the root and the cwd arguments. It's still possible to pass the cwd as an optimization. localrepo.pathto is a convenience function that just calls dirstate.pathto, just like localrepo.getcwd. dirstate.pathto becomes a single point that converts most (all?) paths from the internal representation to some OS-specific relative path for display purposes.

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