add an on-select command

This command is executed whenever the selection changes.

app.go

@@ -59,10 +59,8 @@ func newApp(ui *ui, nav *nav) *app {
 }
 
 func (app *app) quit() {
-	if gOpts.history {
-		if err := app.writeHistory(); err != nil {
-			log.Printf("writing history file: %s", err)
-		}
+	if err := app.writeHistory(); err != nil {
+		log.Printf("writing history file: %s", err)
 	}
 	if !gSingleMode {
 		if err := remote(fmt.Sprintf("drop %d", gClientID)); err != nil {
@@ -407,7 +405,7 @@ func (app *app) loop() {
 			curr, err := app.nav.currFile()
 			if err == nil {
 				if d.path == app.nav.currDir().path {
-					app.ui.loadFile(app.nav, true)
+					app.ui.loadFile(app, true)
 				}
 				if d.path == curr.path {
 					app.ui.dirPrev = d
@@ -456,7 +454,7 @@ func (app *app) loop() {
 			app.ui.draw(app.nav)
 		case <-app.ticker.C:
 			app.nav.renew()
-			app.ui.loadFile(app.nav, false)
+			app.ui.loadFile(app, false)
 			app.ui.draw(app.nav)
 		}
 	}
@@ -528,7 +526,7 @@ func (app *app) runShell(s string, args []string, prefix string) {
 		anyKey()
 	}
 
-	app.ui.loadFile(app.nav, true)
+	app.ui.loadFile(app, true)
 
 	switch prefix {
 	case "%":

doc.go

@@ -183,6 +183,7 @@ The following special shell commands are used to customize the behavior of lf wh
     delete
     pre-cd
     on-cd
+    on-select
     on-quit
 
 The following commands/keybindings are provided by default:
@@ -886,6 +887,10 @@ This shell command can be defined to be executed before changing a directory.
 
 This shell command can be defined to be executed after changing a directory.
 
+    on-select
+
+This shell command can be defined to be executed after the selection changes.
+
     on-quit
 
 This shell command can be defined to be executed before quit.