Don't load keymap files with other platforms in the suffix

Example: On osx `keymap.cson` and `keymap-darwin.cson` would load. But
`keymap-win32.cson` would not load.

spec/keymap-spec.coffee

@@ -354,6 +354,27 @@ describe "Keymap", ->
       bindings = keymap.keyBindingsForCommandMatchingElement('cultivate', el)
       expect(bindings).toHaveLength 0
 
+  describe "loading platform specific keybindings", ->
+    customKeymap = null
+
+    beforeEach ->
+      resourcePath = temp.mkdirSync('atom')
+      customKeymap = new Keymap({configDirPath, resourcePath})
+
+    afterEach ->
+      customKeymap.destroy()
+
+    it "doesn't load keybindings from other platforms", ->
+      win32FilePath = path.join(resourcePath, "keymaps", "test-win32.cson")
+      darwinFilePath = path.join(resourcePath, "keymaps", "test-darwin.cson")
+      fs.writeFileSync(win32FilePath, '"body": "ctrl-l": "core:win32-move-left"')
+      fs.writeFileSync(darwinFilePath, '"body": "ctrl-l": "core:darwin-move-left"')
+
+      customKeymap.loadBundledKeymaps()
+      keyBindings = customKeymap.keyBindingsForKeystroke('ctrl-l')
+      expect(keyBindings).toHaveLength 1
+      expect(keyBindings[0].command).toBe "core:#{process.platform}-move-left"
+
   describe "when the user keymap file is changed", ->
     it "is reloaded", ->
       keymapFilePath = path.join(configDirPath, "keymap.cson")

src/keymap.coffee

@@ -142,7 +142,13 @@ class Keymap
       @userKeymapFile.on 'contents-changed moved removed', => @loadUserKeymap()
 
   loadDirectory: (directoryPath) ->
-    @load(filePath) for filePath in fs.listSync(directoryPath, ['.cson', '.json'])
+    platforms = ['darwin', 'freebsd', 'linux', 'sunos', 'win32']
+    otherPlatforms = platforms.filter (name) -> name != process.platform
+
+    for filePath in fs.listSync(directoryPath, ['.cson', '.json'])
+      platform = filePath.match(/-(\w+)\.\w+$/)?[1]
+      continue if platform in otherPlatforms
+      @load(filePath)
 
   load: (path) ->
     @add(path, CSON.readFileSync(path))