Add a "shell" pseudo-command to nomulus tool

Add the "shell" command which lets you run multiple other command in a single
session, sparing you the initialization costs for all but the first of them.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188712815

javatests/google/registry/tools/ShellCommandTest.java

@@ -0,0 +1,68 @@
+// Copyright 2018 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 java.nio.charset.StandardCharsets.US_ASCII;
+import static org.mockito.Mockito.mock;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import java.io.ByteArrayInputStream;
+import java.util.ArrayList;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class ShellCommandTest {
+
+  CommandRunner cli = mock(CommandRunner.class);
+
+  public ShellCommandTest() {}
+
+  @Test
+  public void testParsing() {
+    assertThat(ShellCommand.parseCommand("foo bar 123 baz+ // comment \"string data\""))
+        .isEqualTo(new String[] {"foo", "bar", "123", "baz+", "//", "comment", "string data"});
+    assertThat(ShellCommand.parseCommand("\"got \\\" escapes?\""))
+        .isEqualTo(new String[] {"got \" escapes?"});
+    assertThat(ShellCommand.parseCommand("")).isEqualTo(new String[0]);
+  }
+
+  @Test
+  public void testCommandProcessing() {
+    String testData = "test1 foo bar\ntest2 foo bar\n";
+    ImmutableMap<String, Class<? extends Command>> commandMap = ImmutableMap.of();
+    MockCli cli = new MockCli();
+    ShellCommand shellCommand =
+        new ShellCommand(new ByteArrayInputStream(testData.getBytes(US_ASCII)), cli);
+    shellCommand.run();
+    assertThat(cli.calls)
+        .containsExactly(
+            ImmutableList.of("test1", "foo", "bar"), ImmutableList.of("test2", "foo", "bar"))
+        .inOrder();
+  }
+
+  static class MockCli implements CommandRunner {
+    public ArrayList<ImmutableList<String>> calls = new ArrayList<>();
+
+    @Override
+    public void run(String[] args)
+        throws Exception {
+      calls.add(ImmutableList.copyOf(args));
+    }
+  }
+}