t / t4101 / diff.3-2on commit git fetch-pack: do not complain about "no common commits" in an empty repo (8cb560f)
   1--- a/frotz
   2+++ b/frotz
   3@@ -1,3 +1,2 @@
   4 a
   5-c
   6 b
   7\ No newline at end of file