SampleOperator: register a sample search operator

The sample search operator will search for a single change

Change-Id: If5b4cc41e037029d18a0760b83686d4379e7cf1f

src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
index b182159..7a30dc8 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
@@ -34,6 +34,7 @@
 import com.google.gerrit.server.git.validators.MergeValidationListener;
 import com.google.gerrit.server.git.validators.UploadValidationListener;
 import com.google.gerrit.server.plugins.ServerPluginProvider;
+import com.google.gerrit.server.query.change.ChangeQueryBuilder.ChangeOperatorFactory;
 import com.google.gerrit.server.validators.HashtagValidationListener;
 import com.google.inject.AbstractModule;
 
@@ -74,6 +75,10 @@
     DynamicSet.bind(binder(), CommitValidationListener.class)
         .to(CommitValidator.class);
     configurePluginParameters();
+
+    bind(ChangeOperatorFactory.class)
+       .annotatedWith(Exports.named("sample"))
+       .to(SampleOperator.class);
   }
 
   private void configurePluginParameters() {

src/main/java/com/googlesource/gerrit/plugins/cookbook/SampleOperator.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/SampleOperator.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/SampleOperator.java
new file mode 100644
index 0000000..4d11bf9
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/SampleOperator.java
@@ -0,0 +1,53 @@
+// Copyright (C) 2015 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.googlesource.gerrit.plugins.cookbook;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.server.query.OperatorPredicate;
+import com.google.gerrit.server.query.Predicate;
+import com.google.gerrit.server.query.QueryParseException;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.server.query.change.ChangeQueryBuilder;
+
+import com.google.inject.Singleton;
+
+@Singleton
+public class SampleOperator
+    implements ChangeQueryBuilder.ChangeOperatorFactory {
+  public static class MyPredicate extends OperatorPredicate<ChangeData> {
+    private final Change.Id id;
+
+    MyPredicate(Change.Id id) {
+      super("sample", id.toString());
+      this.id = id;
+    }
+
+    @Override
+    public boolean match(ChangeData object) {
+      return id.equals(object.getId());
+    }
+
+    @Override
+    public int getCost() {
+      return 1;
+    }
+  }
+
+  @Override
+  public Predicate<ChangeData> create(ChangeQueryBuilder builder, String value)
+      throws QueryParseException {
+    return new MyPredicate(Change.Id.parse(value));
+  }
+}

src/main/resources/Documentation/change-search-operators.md

diff --git a/src/main/resources/Documentation/change-search-operators.md b/src/main/resources/Documentation/change-search-operators.md
new file mode 100644
index 0000000..78d7bf3
--- /dev/null
+++ b/src/main/resources/Documentation/change-search-operators.md
@@ -0,0 +1,12 @@
+Search Operators
+================
+
+Sample Operator
+---------------
+
+The @PLUGIN@ plugin provides a new `sample_@PLUGIN@` change search operator
+which can search for one specific change by change number.
+
+*sample_@PLUGIN@:number*
+
+Returns changes which match the change number `number`.