: Test for source tree numbering *1: Level A *1+1: Level B *1+2: Level B *1+2*1: Level C *1+3: Level B *1+3*1: Level C *1+3*1*1: Level D *2: Level A *2+1: Level B *2+1*1: Level C *2+1*1*1: Level D *2+1*1*1*1: Level E *3: Level A *3+1: Level B *3+1*1: Level C *3+1*1*1: Level D *3+1*1*1*1: Level E *3+1*1*2: Level D *3+1*1*2*1: Level E *3+1*2: Level C *3+1*2*1: Level D *3+2: Level B