Order group command usage commands

Author: kylef

Commander/Group.swift

@@ -12,7 +12,7 @@ public enum GroupError : ErrorType, CustomStringConvertible {
     case .UnknownCommand(let name):
       return "Unknown command: `\(name)`"
     case .NoCommand(let path, let group):
-      let available = group.commands.keys.joinWithSeparator(", ")
+      let available = group.commands.keys.sort().joinWithSeparator(", ")
       if let path = path {
         return "Usage: \(path) COMMAND\n\nCommands: \(available)"
       } else {

CommanderTests/GroupTests.swift

@@ -153,11 +153,11 @@ class GroupErrorTests : XCTestCase {
 
   func testNoCommandDescription() {
     let error = GroupError.NoCommand("pod lib", group)
-    XCTAssertEqual(error.description, "Usage: pod lib COMMAND\n\nCommands: lint, create")
+    XCTAssertEqual(error.description, "Usage: pod lib COMMAND\n\nCommands: create, lint")
   }
 
   func testNoCommandWithoutPathDescription() {
     let error = GroupError.NoCommand(nil, group)
-    XCTAssertEqual(error.description, "Commands: lint, create")
+    XCTAssertEqual(error.description, "Commands: create, lint")
   }
 }