Service registry: Tree versioning

[mkalam-alami]

See nuxeo/nuxeo-tree-snapshot for the current implementation.

The current versioning system in Nuxeo is limited in that it only allows versioning at document-level ; versioning of folders and their contents is not linked in any way. A more adapted approach to versioning has to be implemented.

Goals

• To be able to rollback a whole system after a bad discovery session
• To let all systems containing a document know when it has been changed
• To allow for retro-compatibility validation features, at System level

Features

• [OK] Thanks to a specific document facet (Snapshotable), enable folder-wise versioning of documents.
  • See tree-snapshot Readme for more detailed spec
• [TODO] Make sure that when a document is updated, all snapshotables that contain it are versioned (note: depends on how 'live proxies' are implemented)
• [TODO] 20120829 Proxy handling : adding a document to a proxy folder should / could add it to its target folder, make test TestSnapshotingAndProxies.testAddAndGetProxyFolderChildren() pass (from README.md)

[mdutoo]

To use it :
get source at https://github.com/nuxeo/nuxeo-tree-snapshot/blob/master/src/test/java/org/nuxeo/snapshot/TestSnapshoting.java
or get jar at https://maven-eu.nuxeo.org/nexus/index.html#nexus-search;quick~tree-snapshot
then do :

    Snapshotable snapshotable = root.getAdapter(Snapshotable.class);
    Snapshot snapshot = snapshotable.createSnapshot(VersioningOption.MINOR);

(from https://github.com/nuxeo/nuxeo-tree-snapshot/blob/master/src/test/java/org/nuxeo/snapshot/TestSnapshoting.java )