How do I get the IContibutor/IContributorHandle of the creator of a changeset using the API?

Accepted answer

I was using:
IChangeSet changeSet = scmChangeset.getSnapshotChangeset((IChangeSetHandle) changeSetHandle);
to get the IChangeSet and this interface does not set author/modifiedBy. Switched to:
IChangeSet changeSet = (IChangeSet) repo.itemManager().fetchCompleteState(changeSetHandle,null);
which provides all properties.
IChangeSet changeSet = scmChangeset.getSnapshotChangeset((IChangeSetHandle) changeSetHandle);
to get the IChangeSet and this interface does not set author/modifiedBy. Switched to:
IChangeSet changeSet = (IChangeSet) repo.itemManager().fetchCompleteState(changeSetHandle,null);
which provides all properties.