Better relative path handling.

The scaled script tries to absolutize paths before it sends them to Scaled, but
we should try to be as sensible as we can in the absence of that help.
Avoid extra work when setting same buffer.
Make Seq.unapplySeq work with SeqV as well.
Avoid Seq.unapplySeq.

I fixed the bug that was causing it to fail, but after looking at the bytecode
generated by that pattern match, I can't, in good conscience, rely on
unapplySeq for anything that might remotely be performance sensitive.