t / t4101 / diff.2-3on commit git-merge-octopus: use (merge-base A (merge B C D E...)) for stepwise merge (c5dc9a2)
   1--- a/frotz
   2+++ b/frotz
   3@@ -1,2 +1,3 @@
   4 a
   5+c
   6 b
   7\ No newline at end of file