Guard against null branch in PullCommand

Throw a NoHeadException when Repository.getFullBranch
returns null

Bug: 351543
Change-Id: I666cd5b67781508a293ae553c6fe5c080c8f4d99
Signed-off-by: Kevin Sawicki <kevin@github.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/PullCommandTest.java

@@ -55,8 +55,11 @@ import java.io.IOException;
 
 import org.eclipse.jgit.api.CreateBranchCommand.SetupUpstreamMode;
 import org.eclipse.jgit.api.MergeResult.MergeStatus;
+import org.eclipse.jgit.api.errors.NoHeadException;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.RepositoryState;
 import org.eclipse.jgit.lib.RepositoryTestCase;
 import org.eclipse.jgit.lib.StoredConfig;
@@ -220,6 +223,15 @@ public class PullCommandTest extends RepositoryTestCase {
 				.getRepositoryState());
 	}
 
+	@Test(expected = NoHeadException.class)
+	public void testPullEmptyRepository() throws Exception {
+		Repository empty = createWorkRepository();
+		RefUpdate delete = empty.updateRef(Constants.HEAD, true);
+		delete.setForceUpdate(true);
+		delete.delete();
+		Git.wrap(empty).pull().call();
+	}
+
 	@Override
 	@Before
 	public void setUp() throws Exception {

org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties

@@ -352,6 +352,7 @@ prefixRemote=remote:
 problemWithResolvingPushRefSpecsLocally=Problem with resolving push ref specs locally: {0}
 progressMonUploading=Uploading {0}
 propertyIsAlreadyNonNull=Property is already non null
+pullOnRepoWithoutHEADCurrentlyNotSupported=Pull on repository without HEAD currently not supported
 pullTaskName=Pull
 pushCancelled=push cancelled
 pushIsNotSupportedForBundleTransport=Push is not supported for bundle transport

org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java

@@ -412,6 +412,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String problemWithResolvingPushRefSpecsLocally;
 	/***/ public String progressMonUploading;
 	/***/ public String propertyIsAlreadyNonNull;
+	/***/ public String pullOnRepoWithoutHEADCurrentlyNotSupported;
 	/***/ public String pullTaskName;
 	/***/ public String pushCancelled;
 	/***/ public String pushIsNotSupportedForBundleTransport;

org.eclipse.jgit/src/org/eclipse/jgit/api/PullCommand.java

@@ -112,7 +112,8 @@ public class PullCommand extends TransportCommand<PullCommand, PullResult> {
 	 */
 	public PullResult call() throws WrongRepositoryStateException,
 			InvalidConfigurationException, DetachedHeadException,
-			InvalidRemoteException, CanceledException, RefNotFoundException {
+			InvalidRemoteException, CanceledException, RefNotFoundException,
+			NoHeadException {
 		checkCallable();
 
 		monitor.beginTask(JGitText.get().pullTaskName, 2);
@@ -120,6 +121,9 @@ public class PullCommand extends TransportCommand<PullCommand, PullResult> {
 		String branchName;
 		try {
 			String fullBranch = repo.getFullBranch();
+			if (fullBranch == null)
+				throw new NoHeadException(
+						JGitText.get().pullOnRepoWithoutHEADCurrentlyNotSupported);
 			if (!fullBranch.startsWith(Constants.R_HEADS)) {
 				// we can not pull if HEAD is detached and branch is not
 				// specified explicitly