patch 8.1.1922: in diff mode global operations can be very slow
Problem: In diff mode global operations can be very slow.
Solution: Do not call diff_redraw() many times, call it once when redrawing.
And also don't update folds multiple times.
diff --git a/src/globals.h b/src/globals.h
index d0837d3..712a739 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1051,6 +1051,9 @@
EXTERN int must_redraw INIT(= 0); // type of redraw necessary
EXTERN int skip_redraw INIT(= FALSE); // skip redraw once
EXTERN int do_redraw INIT(= FALSE); // extra redraw once
+#ifdef FEAT_DIFF
+EXTERN int need_diff_redraw INIT(= 0); // need to call diff_redraw()
+#endif
EXTERN int need_highlight_changed INIT(= TRUE);