t / t4101 / diff.3-1on commit check-ref-format doc: --branch validates and expands <branch> (89dd32a)
   1--- a/frotz
   2+++ b/frotz
   3@@ -1,3 +1,3 @@
   4 a
   5+b
   6 c
   7-b
   8\ No newline at end of file