Add CommandRegistry::findCommands

spec/command-registry-spec.coffee

@@ -111,3 +111,16 @@ describe "CommandRegistry", ->
       grandchild.dispatchEvent(new CustomEvent('command-1', bubbles: true))
       grandchild.dispatchEvent(new CustomEvent('command-2', bubbles: true))
       expect(calls).toEqual []
+
+  describe "::findCommands({target})", ->
+    it "returns commands that can be invoked on the target or its ancestors", ->
+      registry.add '.parent', 'namespace:command-1', ->
+      registry.add '.child', 'namespace:command-2', ->
+      registry.add '.grandchild', 'namespace:command-3', ->
+      registry.add '.grandchild.no-match', 'namespace:command-4', ->
+
+      expect(registry.findCommands(target: grandchild)).toEqual [
+        {name: 'namespace:command-3', displayName: 'Namespace: Command 3'}
+        {name: 'namespace:command-2', displayName: 'Namespace: Command 2'}
+        {name: 'namespace:command-1', displayName: 'Namespace: Command 1'}
+      ]

src/command-registry.coffee

@@ -1,5 +1,6 @@
 {Disposable, CompositeDisposable} = require 'event-kit'
 {specificity} = require 'clear-cut'
+_ = require 'underscore-plus'
 
 SequenceCount = 0
 SpecificityCache = {}
@@ -67,6 +68,22 @@ class CommandRegistry
       break if currentTarget is @rootNode
       currentTarget = currentTarget.parentNode
 
+  findCommands: ({target}) ->
+    commands = []
+    currentTarget = target
+    loop
+      for commandName, listeners of @listenersByCommandName
+        for listener in listeners
+          if currentTarget.webkitMatchesSelector(listener.selector)
+            commands.push
+              name: commandName
+              displayName: _.humanizeEventName(commandName)
+
+      break if currentTarget is @rootNode
+      currentTarget = currentTarget.parentNode
+
+    commands
+
 class CommandListener
   constructor: (@selector, @callback) ->
     @specificity = (SpecificityCache[@selector] ?= specificity(@selector))