diff.diff_master_master^_side

$ git diff master master^ side
diff --cc dir/sub
index cead32e,7289e35..992913c
--- a/dir/sub
+++ b/dir/sub
@@@ -1,6 -1,4 +1,8 @@@
  A
  B
 +C
 +D
 +E
 +F
+ 1
+ 2
diff --cc file0
index b414108,f4615da..10a8a9f
--- a/file0
+++ b/file0
@@@ -1,6 -1,6 +1,9 @@@
  1
  2
  3
 +4
 +5
 +6
+ A
+ B
+ C
$