Adding functionality to unbind keys

* adds new special-case keybinding to remove an existing default key binding.
* hides the show/close help text in the status line when no key is assigned to "ToggleHelp"
* updating documentation

cmd/micro/bindings.go

@@ -346,7 +346,13 @@ func BindKey(k, v string) {
 	if v == "ToggleHelp" {
 		helpBinding = k
 	}
+	if helpBinding == k && v != "ToggleHelp" {
+		helpBinding = ""
+	}
 	
+	if v == "UnbindKey" {
+		delete(bindings, key)
+	} else {
 		actionNames := strings.Split(v, ",")
 		actions := make([]func(*View, bool) bool, 0, len(actionNames))
 		for _, actionName := range actionNames {
@@ -354,6 +360,7 @@ func BindKey(k, v string) {
 		}
 
 		bindings[key] = actions
+	}
 }
 
 // DefaultBindings returns a map containing micro's default keybindings

cmd/micro/statusline.go

@@ -36,10 +36,13 @@ func (sline *Statusline) Display() {
 	// Add the filetype
 	file += " " + sline.view.Buf.FileType()
 
-	rightText := helpBinding + " for help "
+	rightText := ""
+	if len(helpBinding) > 0 {
+		rightText = helpBinding + " for help "
 		if sline.view.Type == vtHelp {
 			rightText = helpBinding + " to close help "
 		}
+	}
 
 	statusLineStyle := defStyle.Reverse(true)
 	if style, ok := colorscheme["statusline"]; ok {

runtime/help/keybindings.md

@@ -115,6 +115,11 @@ and quit you can bind it like so:
 }
 ```
 
+# Unbinding keys
+
+It is also possible to disable any of the default key bindings by use of the 
+`UnbindKey` action in the user's `bindings.json` file.
+
 # Bindable actions and bindable keys
 
 The list of default keybindings contains most of the possible actions and keys
@@ -196,6 +201,7 @@ HSplit
 PreviousSplit
 ToggleMacro
 PlayMacro
+UnbindKey
 ```
 
 Here is the list of all possible keys you can bind: