@Override
    public Void call() throws TTException {
        updateOnly();
        if (mCommit == EShredderCommit.COMMIT) {
            mWtx.commit();
        }
        return null;
    }
@ Override public Void call ( ) throws TTException { updateOnly ( ) ; if ( mCommit == EShredderCommit . COMMIT ) { mWtx . commit ( ) ; } return null ; }
Invoking the shredder.

@throws TTException
if Treetank encounters something went wrong
@return revision of last revision (before commit)