[ZEPPELIN-1352] Refactor Notebook repo versioning to return Revision Empty instead of NULL

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.7.0
• Assignee: Anthony Corbacho
• Reporter: Anthony Corbacho
• Created: 22/Aug/16 02:22
• Updated: 01/Dec/16 16:31
• Resolved: 01/Dec/16 14:25

Description

In Zeppelin notebookRepo, versioning (checkpoint, get, revisionHistory) use to return NULL.

It will be better to return Empty (Revision or list).

Issue Links

• links to: GitHub Pull Request #1338
• links to: GitHub Pull Request #1697