t / t4135 / diff-with spaces.diffon commit xdl_change_compact(): only use heuristic if group can't be matched (cb0eded)
   1--- post image.txt.orig 2010-08-18 20:13:31.544002255 -0500
   2+++ post image.txt      2010-08-18 20:13:31.544002255 -0500
   3@@ -1 +1 @@
   4-preimage
   5+postimage