Arvados

Users want to be able to find their collections, so we should give them the Arvados UUID of the collection object instead of the portable data hash. However, crunch (and possibly other tools) expect to get portable data hashes back from arv-put, so there needs to be a new command line flag for arv-put such as "--portable-data-hash" that continues to implement the current behavior, and tools need to be modified to use that.