Right arrow expands the selected directory in TreeView

src/extensions/tree-view.coffee

@@ -21,6 +21,7 @@ class TreeView extends View
 
     @on 'move-up', => @moveUp()
     @on 'move-down', => @moveDown()
+    @on 'tree-view:expand-directory', => @expandDirectory()
     @rootView.on 'active-editor-path-change', => @selectActiveFile()
 
   selectActiveFile: ->
@@ -45,6 +46,10 @@ class TreeView extends View
     else
       @selectEntry(@find('.entry').last())
 
+  expandDirectory: ->
+    selectedEntry = @selectedEntry()
+    selectedEntry.view().expand() if selectedEntry.is('.directory')
+
   selectedEntry: ->
     @find('.selected')