PushCertificateStore: Return boolean from batch save methods

Change-Id: I9730cb4f60c60ee6d5a7a156a0b6a53f79309ec3

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/PushCertificateStoreTest.java

@@ -49,6 +49,8 @@ import static org.eclipse.jgit.lib.RefUpdate.Result.LOCK_FAILURE;
 import static org.eclipse.jgit.lib.RefUpdate.Result.NEW;
 import static org.eclipse.jgit.lib.RefUpdate.Result.NO_CHANGE;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -277,10 +279,12 @@ public class PushCertificateStoreTest {
 	@Test
 	public void saveInBatch() throws Exception {
 		BatchRefUpdate batch = repo.getRefDatabase().newBatchUpdate();
+		assertFalse(store.save(batch));
+		assertEquals(0, batch.getCommands().size());
 		PushCertificate addMaster = newCert(
 				command(zeroId(), ID1, "refs/heads/master"));
 		store.put(addMaster, newIdent());
-		store.save(batch);
+		assertTrue(store.save(batch));
 
 		List<ReceiveCommand> commands = batch.getCommands();
 		assertEquals(1, commands.size());

org.eclipse.jgit/src/org/eclipse/jgit/transport/PushCertificateStore.java

@@ -394,17 +394,19 @@ public class PushCertificateStore implements AutoCloseable {
 	 *
 	 * @param batch
 	 *            update to save to.
+	 * @return whether a command was added to the batch.
 	 * @throws IOException
 	 *             if there was an error reading from or writing to the
 	 *             repository.
 	 */
-	public void save(BatchRefUpdate batch) throws IOException {
+	public boolean save(BatchRefUpdate batch) throws IOException {
 		ObjectId newId = write();
 		if (newId == null) {
-			return;
+			return false;
 		}
 		batch.addCommand(new ReceiveCommand(
 				commit != null ? commit : ObjectId.zeroId(), newId, REF_NAME));
+		return true;
 	}
 
 	/**