return the smallest key adiff in A such that A[adiff] != B[bdiff]

* Converts a `value_query` in the above grammar, with the given path, to a predicate. */

* Converts a `value_query` in the above grammar, with the given path, to a predicate * The predicate is returned by appending to `out_terms` zero or

FIXME: assumes well encoded FIXME: Create a different version without bounds checking for when we know we're in the middle of an encoded key, so there