t / t4135 / add-with tab.diffon commit test: remove a porcelain test that hard-codes commit names (67a612c)
   1diff -pruN a/post       image.txt b/post        image.txt
   2--- a/post      image.txt       1969-12-31 18:00:00.000000000 -0600
   3+++ b/post      image.txt       2010-08-18 20:13:31.628002255 -0500
   4@@ -0,0 +1 @@
   5+postimage