patch 7.4.2123
Problem:    No new style test for diff mode.
Solution:   Add a test.  Check that folds are in sync.
diff --git a/src/Makefile b/src/Makefile
index 7ef6e90..6d49e90 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2042,7 +2042,7 @@
 	test11 test12 test13 test14 test15 test16 test17 test18 test19 \
 	test20 test21 test22 test23 test24 test25 test26 test27 test28 test29 \
 	test30 test31 test32 test33 test34 test36 test37 test38 test39 \
-	test40 test41 test42 test43 test44 test45 test46 test47 test48 test49 \
+	test40 test41 test42 test43 test44 test45 test46 test48 test49 \
 	test50 test51 test52 test53 test54 test55 test56 test57 test58 test59 \
 	test60 test62 test63 test64 test65 test66 test67 test68 test69 \
 	test70 test71 test72 test73 test74 test75 test76 test77 test78 test79 \
@@ -2064,6 +2064,7 @@
 	test_cscope \
 	test_cursor_func \
 	test_delete \
+	test_diffmode \
 	test_digraph \
 	test_ex_undo \
 	test_execute_func \