There's nothing in the FS spec covering the new API. Add it in a new .md file
- add FS model with the notion of a function mapping (uploadID -> Upload), the operations (list, commit, abort). The TLA+ model of
HADOOP-13786shows how to do this.
- Contract tests of not just the successful path, but all the invalid ones.
- implementations of the contract tests of all FSs which support the new API.