Add a Nomulus command to list Datastore operations

Command would be useful when checking the status of daily
backup jobs.

Only two modes are supported: list all operations, or list those
that started within the past period as specified by command line
option.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=229239783

javatests/google/registry/tools/ListDatastoreOperationsCommandTest.java

@@ -0,0 +1,74 @@
+// Copyright 2019 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.tools;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import google.registry.export.datastore.DatastoreAdmin;
+import google.registry.export.datastore.DatastoreAdmin.ListOperations;
+import google.registry.export.datastore.Operation.OperationList;
+import google.registry.testing.FakeClock;
+import google.registry.util.Clock;
+import java.io.IOException;
+import org.joda.time.DateTime;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+
+/** Unit tests for {@link google.registry.tools.ListDatastoreOperationsCommand}. */
+@RunWith(JUnit4.class)
+public class ListDatastoreOperationsCommandTest
+    extends CommandTestCase<ListDatastoreOperationsCommand> {
+
+  @Mock private DatastoreAdmin datastoreAdmin;
+  @Mock private ListOperations listOperationsRequest;
+  @Captor ArgumentCaptor<String> filterClause;
+
+  private final Clock clock = new FakeClock(new DateTime("2019-01-01T00:00:30Z"));
+
+  @Before
+  public void setup() throws IOException {
+    command.datastoreAdmin = datastoreAdmin;
+    command.clock = clock;
+
+    when(datastoreAdmin.list(filterClause.capture())).thenReturn(listOperationsRequest);
+    when(datastoreAdmin.listAll()).thenReturn(listOperationsRequest);
+    when(listOperationsRequest.execute()).thenReturn(new OperationList());
+  }
+
+  @Test
+  public void testListAll() throws Exception {
+    runCommand();
+    verify(datastoreAdmin, times(1)).listAll();
+    verifyNoMoreInteractions(datastoreAdmin);
+  }
+
+  @Test
+  public void testListWithFilter() throws Exception {
+    runCommand("--start_time_filter=PT30S");
+    verify(datastoreAdmin, times(1)).list(filterClause.capture());
+    assertThat(filterClause.getValue())
+        .isEqualTo("metadata.common.startTime>\"2019-01-01T00:00:00.000Z\"");
+    verifyNoMoreInteractions(datastoreAdmin);
+  }
+}