Major Description
Currently Root.commit takes a message argument of type string. This is used in a single place for looping through the user data for observation, which stretches the initial intention. OTOH we might need a way to convey additional information from Root.commit to the commit validators (e.g. for OAK-1424). I therefore suggest to replace the message parameter with a info parameter of type Map<String, Object>:
/**
* Atomically persists all changes made to the tree attached to this root.
* <p>
* If {@code info} contains a mapping for {@link #COMMIT_PATH} and the
* associated value is a string, implementations may throw a
* {@code CommitFailedException} if there are changes outside of the subtree
* designated by that path and the implementation does not support
* such partial commits. However all implementation must handler the
* case where a {@code path} designates a subtree that contains all
* unpersisted changes.
* <p>
* The {@code info} map is passed to the underlying storage
* as a part of the internal commit information attached to this commit.
* The commit information will be made available to local observers but
* will not be visible to observers on other cluster nodes.
* <p>
* After a successful operation the root is automatically
* {@link #refresh() refreshed}, such that trees previously obtained
* through {@link #getTree(String)} may become non existing.
*/
void commit(Map<String, Object> info) throws CommitFailedException;