patch 8.2.0662: cannot use input() in a channel callback
Problem: Cannot use input() in a channel callback.
Solution: Reset vgetc_busy. (closes #6010)
diff --git a/src/globals.h b/src/globals.h
index 725493b..2dceab5 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1814,6 +1814,9 @@
EXTERN int did_add_timer INIT(= FALSE);
EXTERN int timer_busy INIT(= 0); // when timer is inside vgetc() then > 0
#endif
+#ifdef FEAT_EVAL
+EXTERN int input_busy INIT(= 0); // when inside get_user_input() then > 0
+#endif
#ifdef FEAT_BEVAL_TERM
EXTERN int bevalexpr_due_set INIT(= FALSE);