Add 'User-Agent' header to CLI REST calls

Update the InitializrService so that a 'SpringBootCli' User-Agent header
is sent with each request. This should allow the server-side code to
gracefully evolve the JSON format if needed.

Fixes gh-1869

spring-boot-cli/src/main/java/org/springframework/boot/cli/command/init/InitializrService.java

@@ -141,6 +141,8 @@ class InitializrService {
 	private CloseableHttpResponse execute(HttpUriRequest request, Object url,
 			String description) {
 		try {
+			request.addHeader("User-Agent", "SpringBootCli/"
+					+ getClass().getPackage().getImplementationVersion());
 			return getHttp().execute(request);
 		}
 		catch (IOException ex) {

spring-boot-cli/src/test/java/org/springframework/boot/cli/command/init/InitCommandTests.java

@@ -26,15 +26,24 @@ import java.util.zip.ZipOutputStream;
 
 import joptsimple.OptionSet;
 
+import org.apache.http.Header;
+import org.apache.http.client.methods.HttpUriRequest;
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.MockitoAnnotations;
 import org.springframework.boot.cli.command.status.ExitStatus;
 
+import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link InitCommand}
@@ -50,6 +59,14 @@ public class InitCommandTests extends AbstractHttpClientMockTests {
 
 	private final InitCommand command;
 
+	@Captor
+	private ArgumentCaptor<HttpUriRequest> requestCaptor;
+
+	@Before
+	public void setupMocks() {
+		MockitoAnnotations.initMocks(this);
+	}
+
 	public InitCommandTests() {
 		InitializrService initializrService = new InitializrService(this.http);
 		this.handler = new TestableInitCommandOptionHandler(initializrService);
@@ -276,6 +293,14 @@ public class InitCommandTests extends AbstractHttpClientMockTests {
 		assertEquals(ExitStatus.ERROR, this.command.run("foobar", "barfoo"));
 	}
 
+	@Test
+	public void userAgent() throws Exception {
+		this.command.run("--list", "--target=http://fake-service");
+		verify(this.http).execute(this.requestCaptor.capture());
+		Header agent = this.requestCaptor.getValue().getHeaders("User-Agent")[0];
+		assertThat(agent.getValue(), startsWith("SpringBootCli/"));
+	}
+
 	private byte[] createFakeZipArchive(String fileName, String content)
 			throws IOException {
 		ByteArrayOutputStream bos = new ByteArrayOutputStream();