t / t4101 / diff.3-2on commit check-ref-format doc: de-emphasize the implementation detail of a ref (a0a7e9e)
   1--- a/frotz
   2+++ b/frotz
   3@@ -1,3 +1,2 @@
   4 a
   5-c
   6 b
   7\ No newline at end of file