Add specs for status bar branch label

spec/app/status-bar-spec.coffee

@@ -102,3 +102,19 @@ describe "StatusBar", ->
     it "updates the cursor position in the status bar", ->
       editor.setCursorScreenPosition([1, 2])
       expect(statusBar.cursorPosition.text()).toBe '2,3'
+
+  describe "branch label", ->
+    beforeEach ->
+      rootView.attachToDom()
+
+    it "displays the current branch for files in repositories", ->
+      path = require.resolve('fixtures/git/master.git/HEAD')
+      rootView.open(path)
+      expect(statusBar.branchArea).toBeVisible()
+      expect(statusBar.branchLabel.text()).toBe 'master'
+
+    it "doesn't display the current branch for a file not in a repository", ->
+      path = require.resolve('fixtures/git/nohead.git/HEAD')
+      rootView.open(path)
+      expect(statusBar.branchArea).toBeHidden()
+      expect(statusBar.branchLabel.text()).toBe ''

src/app/status-bar.coffee

@@ -60,10 +60,10 @@ class StatusBar extends View
     if path = @editor.getPath()
       @head = new Git(path).getShortHead()
     else
-      @head = null
+      @head = ''
 
+    @branchLabel.text(@head)
     if @head
-      @branchLabel.text(@head)
       @branchArea.show()
     else
       @branchArea.hide()