vim-patch:8.2.3461: distinguish Normal and Terminal-Normal mode #15878

Problem:    Cannot distinguish Normal and Terminal-Normal mode.
Solution:   Make mode() return "nt" for Terminal-Normal mode. (issue vim/vim#8856)
72406a4bd2

src/nvim/state.c

@@ -195,6 +195,8 @@ char *get_mode(void)
                || restart_edit == 'V') {
       buf[1] = 'i';
       buf[2] = (char)restart_edit;
+    } else if (curbuf->terminal) {
+      buf[1] = 't';
     }
   }