Add 'one' event

Close #2629
Close #2494
Close #459

src/options.go

@@ -622,6 +622,8 @@ func parseKeyChordsImpl(str string, message string, exit func(string)) map[tui.E
 			add(tui.Load)
 		case "focus":
 			add(tui.Focus)
+		case "one":
+			add(tui.One)
 		case "alt-enter", "alt-return":
 			chords[tui.CtrlAltKey('m')] = key
 		case "alt-space":

src/terminal.go

@@ -932,6 +932,12 @@ func (t *Terminal) UpdateList(merger *Merger, reset bool) {
 			t.cy = count - util.Min(count, t.maxItems()) + pos
 		}
 	}
+	if !t.reading && t.merger.Length() == 1 {
+		one := tui.One.AsEvent()
+		if _, prs := t.keymap[one]; prs {
+			t.eventChan <- one
+		}
+	}
 	t.mutex.Unlock()
 	t.reqBox.Set(reqInfo, nil)
 	t.reqBox.Set(reqList, nil)

src/tui/tui.go

@@ -93,6 +93,7 @@ const (
 	Start
 	Load
 	Focus
+	One
 
 	AltBS