: Test for source tree numbering **A**: Level A **A.A**: Level B **A.B**: Level B **A.B.A**: Level C **A.C**: Level B **A.C.A**: Level C **A.C.A.A**: Level D **B**: Level A **B.A**: Level B **B.A.A**: Level C **B.A.A.A**: Level D **B.A.A.A.A**: Level E **C**: Level A **C.A**: Level B **C.A.A**: Level C **C.A.A.A**: Level D **C.A.A.A.A**: Level E **C.A.A.B**: Level D **C.A.A.B.A**: Level E **C.A.B**: Level C **C.A.B.A**: Level D **C.B**: Level B