t / t4135 / git-plain.diffon commit refs: move head_ref{,_submodule} to the common code (2bf68ed)
   1diff --git a/postimage.txt b/postimage.txt
   2new file mode 100644
   3index 0000000..eff0c54
   4--- /dev/null
   5+++ b/postimage.txt
   6@@ -0,0 +1 @@
   7+postimage