[PATCH] Fix LTREE subpath with negative offset

Marcus Gartner <m.a.gartner@gmail.com> writes:

subpath(ltree,offset,len) now correctly errors when given an offset less
than -n where n is the number of labels in the given ltree. A duplicate
block of code has been removed which allowed an offset as low as -2n.

Nice catch ... as far as I can see from the git history, that mistake
has been there since day one.

I'm inclined to put this in master only, without a back-patch.
It's not fixing any case that should work, and it seems possible
that somebody out there is depending on the bogus behavior.

regards, tom lane