patch 8.1.2289: after :diffsplit closing the window does not disable diff
Problem: After :diffsplit closing the window does not disable diff.
Solution: Add "closeoff" to 'diffopt' and add it to the default.
diff --git a/src/optiondefs.h b/src/optiondefs.h
index 05e0406..881ec06 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -846,7 +846,8 @@
|P_NODUP,
#ifdef FEAT_DIFF
(char_u *)&p_dip, PV_NONE,
- {(char_u *)"internal,filler", (char_u *)NULL}
+ {(char_u *)"internal,filler,closeoff",
+ (char_u *)NULL}
#else
(char_u *)NULL, PV_NONE,
{(char_u *)"", (char_u *)NULL}