remove duplicate context menu entries

spec/context-menu-manager-spec.coffee

@@ -17,6 +17,19 @@ describe "ContextMenuManager", ->
       expect(contextMenu.definitions['.selector'][0].label).toEqual 'label'
       expect(contextMenu.definitions['.selector'][0].command).toEqual 'command'
 
+    it 'does not load duplicates',  ->
+      contextMenu.add 'file-path',
+        '.selector':
+          'label': 'command'
+
+      contextMenu.add 'file-path',
+        '.selector':
+          'another label': 'command'
+
+      expect(contextMenu.definitions['.selector'][0].label).toEqual 'label'
+      expect(contextMenu.definitions['.selector'][0].command).toEqual 'command'
+      expect(contextMenu.definitions['.selector'][1]).toBeUndefined()
+
     it "loads submenus", ->
       contextMenu.add 'file-path',
         '.selector':

src/context-menu-manager.coffee

@@ -60,7 +60,8 @@ class ContextMenuManager
   #              editor is in dev mode.
   addBySelector: (selector, definition, {devMode}={}) ->
     definitions = if devMode then @devModeDefinitions else @definitions
-    (definitions[selector] ?= []).push(definition)
+    unless _.findWhere(definitions[selector], command: definition.command)
+      (definitions[selector] ?= []).push(definition)
 
   # Returns definitions which match the element and devMode.
   definitionsForElement: (element, {devMode}={}) ->