Add @Options annotation

Support using @Option annotations from other objects during command
line parsing so that options can be shared by different classes
using composition instead of inheritance.

Change-Id: I949ae8387847057301e22bd2b2be77d1dc3c25aa

gerrit-util-cli/src/main/java/com/google/gerrit/util/cli/Options.java

@@ -0,0 +1,33 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.util.cli;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Marks a field that refers to a class with @Option annotations
+ *
+ * <p>Any @Option annotations found on the referred class will be handled as if they were found on
+ * the referring class.
+ */
+@Retention(RUNTIME)
+@Target({FIELD})
+public @interface Options {
+  String prefix() default "";
+}