RevCommit m0 = master.commit().add("m", ",m0").message("m0").create();
RevCommit m1 = master.commit().add("m", "m1").message("m1").create();
db_t.getRevWalk().parseCommit(m1);
BranchBuilder side = db_t.branch("side");
RevCommit s1 = side.commit().parent(m0).add("s", "s1").message("s1")
.create();
RevCommit s2 = side.commit().parent(m1).add("m", "m1")
.message("s2(merge)").create();
RevCommit m2 = master.commit().parent(s1).add("s", "s1")
.message("m2(merge)").create();