implement Pathname#join() interface for Filepath.

lib/jenkins/filepath.rb

@@ -16,6 +16,10 @@ module Jenkins
       FilePath.new(@native.child(name))
     end
 
+    def join(*names)
+      FilePath.new names.inject(@native) {|native, name| native.child(name) }
+    end
+
     def to_s
       @native.getRemote()
     end

spec/jenkins/filepath_spec.rb

@@ -17,6 +17,12 @@ describe Jenkins::FilePath do
     (create(".") + "foo" + "bar").to_s.should == "foo/bar"
   end
 
+  it "returns child for join" do
+    create('.').join('foo').to_s.should == "foo"
+    create('.').join('foo', 'bar').to_s.should == "foo/bar"
+    create('.').join('foo', 'bar', 'baz').to_s.should == "foo/bar/baz"
+  end
+
   it "returns path for to_s" do
     create(".").to_s.should == "."
   end