Improve files_decorator performance

**How?**
Previously the files_decorator inserted parent folders inefficiently.
It started at the first part and ensured each was inserted.

Since the file entries are given to use in alphabetical order, we can
start at the last part of the blob's parents. If this exists, we can
short circuit and be done inserting parents.

**What else?**
- Improve performance of decorateData. The object spread operator is
not needed because the object is brand new.