Allowed to change description of a command in CommandSet

lib/pry/command_set.rb

@@ -102,5 +102,17 @@ class Pry
         raise NoCommandError.new(name, self)
       end
     end
+
+    # Sets the description for a command (replacing the old
+    # description.)
+    # @param [String] name The command name.
+    # @param [String] description The command description.
+    # @example
+    #   MyCommands = Pry::CommandSet.new :test do
+    #     desc "help", "help description"
+    #   end
+    def desc(name, description)
+      commands[name].description = description
+    end
   end
 end

test/test.rb

@@ -904,4 +904,11 @@ describe Pry::CommandSet do
     @set.run_command nil, 'bar'
     run.should == true
   end
+
+  it 'should be able to change the descritpions of methods' do
+    @set.command('foo', 'bar') {}
+    @set.desc 'foo', 'baz'
+
+    @set.commands['foo'].description.should == 'baz'
+  end
 end