add unmark command to unmark all selections

Mentioned in #79.

comp.go

@@ -27,6 +27,7 @@ var (
 		"bot",
 		"toggle",
 		"invert",
+		"unmark",
 		"yank",
 		"delete",
 		"put",

doc.go

@@ -25,6 +25,7 @@ The following commands are provided by lf with default keybindings:
     bot               (default 'G')
     toggle            (default '<space>')
     invert            (default 'v')
+    unmark            (default 'u')
     yank              (default 'y')
     delete            (default 'd')
     put               (default 'p')

docstring.go

@@ -29,6 +29,7 @@ The following commands are provided by lf with default keybindings:
     bot               (default 'G')
     toggle            (default '<space>')
     invert            (default 'v')
+    unmark            (default 'u')
     yank              (default 'y')
     delete            (default 'd')
     put               (default 'p')

eval.go

@@ -293,12 +293,14 @@ func (e *callExpr) eval(app *app, args []string) {
 		app.ui.loadFileInfo(app.nav)
 	case "invert":
 		app.nav.invert()
+	case "unmark":
+		app.nav.unmark()
 	case "yank":
 		if err := app.nav.save(true); err != nil {
 			app.ui.printf("yank: %s", err)
 			return
 		}
-		app.nav.marks = make(map[string]int)
+		app.nav.unmark()
 		if err := sendRemote("send sync"); err != nil {
 			app.ui.printf("yank: %s", err)
 		}
@@ -307,7 +309,7 @@ func (e *callExpr) eval(app *app, args []string) {
 			app.ui.printf("delete: %s", err)
 			return
 		}
-		app.nav.marks = make(map[string]int)
+		app.nav.unmark()
 		if err := sendRemote("send sync"); err != nil {
 			app.ui.printf("delete: %s", err)
 		}

nav.go

@@ -390,6 +390,11 @@ func (nav *nav) invert() {
 	}
 }
 
+func (nav *nav) unmark() {
+	nav.marks = make(map[string]int)
+	nav.markInd = 0
+}
+
 func (nav *nav) save(copy bool) error {
 	if len(nav.marks) == 0 {
 		curr, err := nav.currFile()

opts.go

@@ -65,6 +65,7 @@ func init() {
 	gOpts.keys["G"] = &callExpr{"bot", nil}
 	gOpts.keys["<space>"] = &callExpr{"toggle", nil}
 	gOpts.keys["v"] = &callExpr{"invert", nil}
+	gOpts.keys["u"] = &callExpr{"unmark", nil}
 	gOpts.keys["y"] = &callExpr{"yank", nil}
 	gOpts.keys["d"] = &callExpr{"delete", nil}
 	gOpts.keys["c"] = &callExpr{"clear", nil}