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/proto/diff.pro b/src/proto/diff.pro
index d6ab221..2ab6c54 100644
--- a/src/proto/diff.pro
+++ b/src/proto/diff.pro
@@ -4,6 +4,7 @@
void diff_buf_add(buf_T *buf);
void diff_invalidate(buf_T *buf);
void diff_mark_adjust(linenr_T line1, linenr_T line2, long amount, long amount_after);
+void diff_redraw(int dofold);
int diff_internal(void);
void ex_diffupdate(exarg_T *eap);
void ex_diffpatch(exarg_T *eap);