t / t5100 / patch0017on commit diff.c: factor advance_or_nullify out of mark_color_as_moved (e2fe6ab)
   1diff --git a/foo b/foo
   2index e69de29..d95f3ad 100644
   3--- a/foo
   4+++ b/foo
   5@@ -0,0 +1 @@
   6+New content