Right arrow expands the selected directory in TreeView

spec/extensions/tree-view-spec.coffee

@@ -179,3 +179,17 @@ describe "TreeView", ->
           treeView.trigger 'move-up'
           expect(rootDirectoryView).toHaveClass 'selected'
 
+    describe "tree-view:expand-directory", ->
+      describe "when a directory entry is selected", ->
+        it "expands the current directory", ->
+          subdir = rootDirectoryView.find('.directory:first')
+          subdir.click()
+
+          expect(subdir).not.toHaveClass 'expanded'
+          treeView.trigger 'tree-view:expand-directory'
+          expect(subdir).toHaveClass 'expanded'
+
+      describe "when a file entry is selected", ->
+        it "does nothing", ->
+          rootDirectoryView.find('.file').click()
+          treeView.trigger 'tree-view:expand-directory'

src/app/keymaps/tree-view.coffee

@@ -0,0 +1,4 @@
+window.keymap.bindKeys '.tree-view'
+  'right': 'tree-view:expand-directory'
+  'left': 'tree-view:contract-directory'
+

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')