patch 8.0.1361: some users don't want to diff with hidden buffers
Problem: Some users don't want to diff with hidden buffers.
Solution: Add the "hiddenoff" item to 'diffopt'. (Alisue, closes #2394)
diff --git a/src/proto/diff.pro b/src/proto/diff.pro
index 7186401..f1afeec 100644
--- a/src/proto/diff.pro
+++ b/src/proto/diff.pro
@@ -16,6 +16,7 @@
void diff_set_topline(win_T *fromwin, win_T *towin);
int diffopt_changed(void);
int diffopt_horizontal(void);
+int diffopt_hiddenoff(void);
int diff_find_change(win_T *wp, linenr_T lnum, int *startp, int *endp);
int diff_infold(win_T *wp, linenr_T lnum);
void nv_diffgetput(int put, long count);