ncdu: added a "refresh" key - for #2174

Added Control+L key to refresh screen. Not sure if this is the
best choice, but it appears to be somewhat common.

cmd/ncdu/ncdu.go

@@ -64,6 +64,7 @@ var helpText = []string{
 	" c toggle counts",
 	" g toggle graph",
 	" n,s,C sort by name,size,count",
+	" ^L refresh screen",
 	" ? to toggle help on and off",
 	" q/ESC/c-C to quit",
 }
@@ -539,6 +540,14 @@ outer:
 					u.toggleSort(&u.sortByCount)
 				case '?':
 					u.togglePopupBox(helpText)
+
+				// Refresh the screen. Not obvious what key to map
+				// this onto, but ^L is a common choice.
+				case termbox.KeyCtrlL:
+					err := termbox.Sync()
+					if err != nil {
+						fs.Errorf(nil, "termbox sync returned error: %v", err)
+					}
 				}
 			}
 		}

docs/content/commands/rclone_ncdu.md

@@ -30,6 +30,7 @@ Here are the keys - press '?' to toggle the help on and off
      c toggle counts
      g toggle graph
      n,s,C sort by name,size,count
+     ^L refresh screen
      ? to toggle help on and off
      q/ESC/c-C to quit