@Override
public RevWalk fetchAndCreateNewRevsWalk(Repository repository, String branch) throws Exception {
	List<ObjectId> currentRemoteRefs = new ArrayList<ObjectId>(); 
	for (Ref ref : repository.getAllRefs().values()) {
		String refName = ref.getName();
		if (refName.startsWith(REMOTE_REFS_PREFIX)) {
			currentRemoteRefs.add(ref.getObjectId());
		}
	}
	
	List<TrackingRefUpdate> newRemoteRefs = this.fetch(repository);
	
	RevWalk walk = new RevWalk(repository);
	for (TrackingRefUpdate newRef : newRemoteRefs) {
		if (branch == null || newRef.getLocalName().endsWith("/" + branch)) {
			walk.markStart(walk.parseCommit(newRef.getNewObjectId()));
		}
	}
	for (ObjectId oldRef : currentRemoteRefs) {
		walk.markUninteresting(walk.parseCommit(oldRef));
	}
	walk.setRevFilter(commitsFilter);
	return walk;
}
 

private List<TrackingRefUpdate> fetch(Repository repository) throws Exception {
	this.logger.info("Fetching changes of repository " + repository.getDirectory().toString());
       try (Git git = new Git(repository)) {
   		FetchResult result = git.fetch().call();
   		
   		Collection<TrackingRefUpdate> updates = result.getTrackingRefUpdates();
   		List<TrackingRefUpdate> remoteRefsChanges = new ArrayList<TrackingRefUpdate>();
   		for (TrackingRefUpdate update : updates) {
   			String refName = update.getLocalName();
   			if (refName.startsWith(REMOTE_REFS_PREFIX)) {
   				ObjectId newObjectId = update.getNewObjectId();
   				this.logger.info(refName +" is now at " + newObjectId.getName());
   				remoteRefsChanges.add(update);
   			}
   		}
   		if (updates.isEmpty()) {
   			this.logger.info("Nothing changed");
   		}
   		return remoteRefsChanges;
       }
}
 

static IStatus handleFetchResult(FetchResult fetchResult) {
	// handle result
	for (TrackingRefUpdate updateRes : fetchResult.getTrackingRefUpdates()) {
		Result res = updateRes.getResult();
		switch (res) {
		case NOT_ATTEMPTED:
		case NO_CHANGE:
		case NEW:
		case FORCED:
		case FAST_FORWARD:
		case RENAMED:
			// do nothing, as these statuses are OK
			break;
		case REJECTED:
			return new Status(IStatus.WARNING, GitActivator.PI_GIT, "Fetch rejected, not a fast-forward.");
		case REJECTED_CURRENT_BRANCH:
			return new Status(IStatus.WARNING, GitActivator.PI_GIT, "Rejected because trying to delete the current branch.");
		default:
			return new Status(IStatus.ERROR, GitActivator.PI_GIT, res.name());
		}
	}
	return Status.OK_STATUS;
}
 

private List<TrackingRefUpdate> fetch(Repository repository) throws Exception {
       logger.info("Fetching changes of repository {}", repository.getDirectory().toString());
       try (Git git = new Git(repository)) {
   		FetchResult result = git.fetch().call();
   		
   		Collection<TrackingRefUpdate> updates = result.getTrackingRefUpdates();
   		List<TrackingRefUpdate> remoteRefsChanges = new ArrayList<TrackingRefUpdate>();
   		for (TrackingRefUpdate update : updates) {
   			String refName = update.getLocalName();
   			if (refName.startsWith(REMOTE_REFS_PREFIX)) {
   				ObjectId newObjectId = update.getNewObjectId();
   				logger.info("{} is now at {}", refName, newObjectId.getName());
   				remoteRefsChanges.add(update);
   			}
   		}
   		if (updates.isEmpty()) {
   			logger.info("Nothing changed");
   		}
   		return remoteRefsChanges;
       }
}
 

public RevWalk fetchAndCreateNewRevsWalk(Repository repository, String branch) throws Exception {
	List<ObjectId> currentRemoteRefs = new ArrayList<ObjectId>(); 
	for (Ref ref : repository.getRefDatabase().getRefs()) {
		String refName = ref.getName();
		if (refName.startsWith(REMOTE_REFS_PREFIX)) {
			currentRemoteRefs.add(ref.getObjectId());
		}
	}
	
	List<TrackingRefUpdate> newRemoteRefs = this.fetch(repository);
	
	RevWalk walk = new RevWalk(repository);
	for (TrackingRefUpdate newRef : newRemoteRefs) {
		if (branch == null || newRef.getLocalName().endsWith("/" + branch)) {
			walk.markStart(walk.parseCommit(newRef.getNewObjectId()));
		}
	}
	for (ObjectId oldRef : currentRemoteRefs) {
		walk.markUninteresting(walk.parseCommit(oldRef));
	}
	walk.setRevFilter(commitsFilter);
	return walk;
}
 

GitTransportUpdate (URIish uri, TrackingRefUpdate update) {
    this.localName = stripRefs(update.getLocalName());
    this.remoteName = stripRefs(update.getRemoteName());
    this.oldObjectId = update.getOldObjectId() == null || ObjectId.zeroId().equals(update.getOldObjectId()) ? null : update.getOldObjectId().getName();
    this.newObjectId = update.getNewObjectId() == null || ObjectId.zeroId().equals(update.getNewObjectId()) ? null : update.getNewObjectId().getName();
    this.result = GitRefUpdateResult.valueOf((update.getResult() == null 
            ? RefUpdate.Result.NOT_ATTEMPTED 
            : update.getResult()).name());
    this.uri = uri.toString();
    this.type = getType(update.getLocalName());
}
 

/**
 * Deletes local branches if corresponding remote branch was removed.
 * @param trackingRefUpdates list of tracking ref updates
 * @param git git instance
 * @return list of deleted branches
 */
private Collection<String> deleteUntrackedLocalBranches(
		Collection<TrackingRefUpdate> trackingRefUpdates, Git git) {
	if (CollectionUtils.isEmpty(trackingRefUpdates)) {
		return Collections.emptyList();
	}

	Collection<String> branchesToDelete = new ArrayList<>();
	for (TrackingRefUpdate trackingRefUpdate : trackingRefUpdates) {
		ReceiveCommand receiveCommand = trackingRefUpdate.asReceiveCommand();
		if (receiveCommand.getType() == DELETE) {
			String localRefName = trackingRefUpdate.getLocalName();
			if (StringUtils.startsWithIgnoreCase(localRefName,
					LOCAL_BRANCH_REF_PREFIX)) {
				String localBranchName = localRefName.substring(
						LOCAL_BRANCH_REF_PREFIX.length(), localRefName.length());
				branchesToDelete.add(localBranchName);
			}
		}
	}

	if (CollectionUtils.isEmpty(branchesToDelete)) {
		return Collections.emptyList();
	}

	try {
		// make sure that deleted branch not a current one
		checkout(git, this.defaultLabel);
		return deleteBranches(git, branchesToDelete);
	}
	catch (Exception ex) {
		String message = format("Failed to delete %s branches.", branchesToDelete);
		warn(message, ex);
		return Collections.emptyList();
	}
}
 

/**
 * Check references updates for any errors
 *
 * @param errorPrefix The error prefix for any error message
 * @param refUpdates A collection of tracking references updates
 */
public static void validateTrackingRefUpdates(String errorPrefix, Collection<TrackingRefUpdate> refUpdates) {
        for (TrackingRefUpdate refUpdate : refUpdates) {
                RefUpdate.Result result = refUpdate.getResult();

                if (result == RefUpdate.Result.IO_FAILURE ||
                    result == RefUpdate.Result.LOCK_FAILURE ||
                    result == RefUpdate.Result.REJECTED ||
                    result == RefUpdate.Result.REJECTED_CURRENT_BRANCH ) {
                        throw new BuildException(String.format("%s - Status '%s'", errorPrefix, result.name()));
                }
        }
}
 

@Override
public GitTransportUpdate createTransportUpdate (URIish urI, TrackingRefUpdate update) {
    return new GitTransportUpdate(urI, update);
}
 

public void testPushRejectNonFastForward () throws Exception {
    String remoteUri = getRemoteRepository().getWorkTree().toURI().toString();
    assertEquals(0, getClient(workDir).listRemoteBranches(remoteUri, NULL_PROGRESS_MONITOR).size());
    File f = new File(workDir, "f");
    add(f);
    String id = getClient(workDir).commit(new File[] { f }, "bbb", null, null, NULL_PROGRESS_MONITOR).getRevision();
    Map<String, GitTransportUpdate> updates = getClient(workDir).push(remoteUri, Arrays.asList(new String[] { "refs/heads/master:refs/heads/master" }), Collections.<String>emptyList(), NULL_PROGRESS_MONITOR).getRemoteRepositoryUpdates();
    Map<String, GitBranch> remoteBranches = getClient(workDir).listRemoteBranches(remoteUri, NULL_PROGRESS_MONITOR);
    assertEquals(1, remoteBranches.size());
    assertEquals(id, remoteBranches.get("master").getId());
    assertEquals(1, updates.size());
    assertUpdate(updates.get("master"), "master", "master", id, null, new URIish(remoteUri).toString(), Type.BRANCH, GitRefUpdateResult.OK);

    // modification
    write(f, "huhu");
    add(f);
    String newid = getClient(workDir).commit(new File[] { f }, "bbb", null, null, NULL_PROGRESS_MONITOR).getRevision();
    updates = getClient(workDir).push(remoteUri, Arrays.asList(new String[] { "refs/heads/master:refs/heads/master" }), Collections.<String>emptyList(), NULL_PROGRESS_MONITOR).getRemoteRepositoryUpdates();
    remoteBranches = getClient(workDir).listRemoteBranches(remoteUri, NULL_PROGRESS_MONITOR);
    assertEquals(1, remoteBranches.size());
    assertEquals(newid, remoteBranches.get("master").getId());
    assertEquals(1, updates.size());
    assertUpdate(updates.get("master"), "master", "master", newid, id, new URIish(remoteUri).toString(), Type.BRANCH, GitRefUpdateResult.OK);
    
    getClient(workDir).createBranch("localbranch", id, NULL_PROGRESS_MONITOR);
    getClient(workDir).checkoutRevision("localbranch", true, NULL_PROGRESS_MONITOR);
    write(f, "huhu2");
    add(f);
    id = getClient(workDir).commit(new File[] { f }, "some change before merge", null, null, NULL_PROGRESS_MONITOR).getRevision();
    updates = getClient(workDir).push(remoteUri, Arrays.asList(new String[] { "+refs/heads/localbranch:refs/heads/master" }), Collections.<String>emptyList(), NULL_PROGRESS_MONITOR).getRemoteRepositoryUpdates();
    remoteBranches = getClient(workDir).listRemoteBranches(remoteUri, NULL_PROGRESS_MONITOR);
    assertEquals(1, remoteBranches.size());
    assertEquals(newid, remoteBranches.get("master").getId());
    assertEquals(1, updates.size());
    assertUpdate(updates.get("master"), "localbranch", "master", id, newid, new URIish(remoteUri).toString(), Type.BRANCH, GitRefUpdateResult.REJECTED_NONFASTFORWARD);
    
    updates = getClient(workDir).push(remoteUri, Arrays.asList(new String[] { "refs/heads/localbranch:refs/heads/master" }), Arrays.asList(new String[] { "+refs/heads/master:refs/remotes/origin/master" }), NULL_PROGRESS_MONITOR).getRemoteRepositoryUpdates();
    remoteBranches = getClient(workDir).listRemoteBranches(remoteUri, NULL_PROGRESS_MONITOR);
    assertEquals(1, remoteBranches.size());
    assertEquals(newid, remoteBranches.get("master").getId());
    assertEquals(1, updates.size());
    assertUpdate(updates.get("master"), "localbranch", "master", id, newid, new URIish(remoteUri).toString(), Type.BRANCH, GitRefUpdateResult.REJECTED_NONFASTFORWARD);
    
    // if starts failing, the WA at GitTransportUpdate.(URIish uri, TrackingRefUpdate update) should be removed
    // this.result = GitRefUpdateResult.valueOf((update.getResult() == null ? RefUpdate.Result.NOT_ATTEMPTED : update.getResult()).name());
    Transport transport = Transport.open(getRepository(getClient(workDir)), new URIish(remoteUri));
    transport.setDryRun(false);
    transport.setPushThin(true);
    PushResult pushResult = transport.push(new DelegatingProgressMonitor(NULL_PROGRESS_MONITOR),
            Transport.findRemoteRefUpdatesFor(getRepository(getClient(workDir)),
            Collections.singletonList(new RefSpec("refs/heads/localbranch:refs/heads/master")),
            Collections.singletonList(new RefSpec("refs/heads/master:refs/remotes/origin/master"))));
    assertEquals(1, pushResult.getTrackingRefUpdates().size());
    for (TrackingRefUpdate update : pushResult.getTrackingRefUpdates()) {
        // null but not NOT_ATTEMPTED, probably a bug
        // remove the WA if it starts failing here
        assertNull(update.getResult());
    }
}
 

private IStatus doPush(IProgressMonitor monitor) throws IOException, CoreException, URISyntaxException, GitAPIException {
	ProgressMonitor gitMonitor = new EclipseGitProgressTransformer(monitor);
	// /git/remote/{remote}/{branch}/file/{path}
	File gitDir = GitUtils.getGitDir(path.removeFirstSegments(2));
	Repository db = null;
	JSONObject result = new JSONObject();
	try {
		db = FileRepositoryBuilder.create(gitDir);
		Git git = Git.wrap(db);

		PushCommand pushCommand = git.push();
		pushCommand.setProgressMonitor(gitMonitor);
		pushCommand.setTransportConfigCallback(new TransportConfigCallback() {
			@Override
			public void configure(Transport t) {
				credentials.setUri(t.getURI());
				if (t instanceof TransportHttp && cookie != null) {
					HashMap<String, String> map = new HashMap<String, String>();
					map.put(GitConstants.KEY_COOKIE, cookie.getName() + "=" + cookie.getValue());
					((TransportHttp) t).setAdditionalHeaders(map);
				}
			}
		});
		RemoteConfig remoteConfig = new RemoteConfig(git.getRepository().getConfig(), remote);
		credentials.setUri(remoteConfig.getURIs().get(0));
		pushCommand.setCredentialsProvider(credentials);

		boolean pushToGerrit = branch.startsWith("for/");
		RefSpec spec = new RefSpec(srcRef + ':' + (pushToGerrit ? "refs/" : Constants.R_HEADS) + branch);
		pushCommand.setRemote(remote).setRefSpecs(spec);
		if (tags)
			pushCommand.setPushTags();
		pushCommand.setForce(force);
		Iterable<PushResult> resultIterable = pushCommand.call();
		if (monitor.isCanceled()) {
			return new Status(IStatus.CANCEL, GitActivator.PI_GIT, "Cancelled");
		}
		PushResult pushResult = resultIterable.iterator().next();
		boolean error = false;
		JSONArray updates = new JSONArray();
		result.put(GitConstants.KEY_COMMIT_MESSAGE, pushResult.getMessages());
		result.put(GitConstants.KEY_UPDATES, updates);
		for (final RemoteRefUpdate rru : pushResult.getRemoteUpdates()) {
			if (monitor.isCanceled()) {
				return new Status(IStatus.CANCEL, GitActivator.PI_GIT, "Cancelled");
			}
			final String rm = rru.getRemoteName();
			// check status only for branch given in the URL or tags
			if (branch.equals(Repository.shortenRefName(rm)) || rm.startsWith(Constants.R_TAGS) || rm.startsWith(Constants.R_REFS + "for/")) {
				JSONObject object = new JSONObject();
				RemoteRefUpdate.Status status = rru.getStatus();
				if (status != RemoteRefUpdate.Status.UP_TO_DATE || !rm.startsWith(Constants.R_TAGS)) {
					object.put(GitConstants.KEY_COMMIT_MESSAGE, rru.getMessage());
					object.put(GitConstants.KEY_RESULT, status.name());
					TrackingRefUpdate refUpdate = rru.getTrackingRefUpdate();
					if (refUpdate != null) {
						object.put(GitConstants.KEY_REMOTENAME, Repository.shortenRefName(refUpdate.getLocalName()));
						object.put(GitConstants.KEY_LOCALNAME, Repository.shortenRefName(refUpdate.getRemoteName()));
					} else {
						object.put(GitConstants.KEY_REMOTENAME, Repository.shortenRefName(rru.getSrcRef()));
						object.put(GitConstants.KEY_LOCALNAME, Repository.shortenRefName(rru.getRemoteName()));
					}
					updates.put(object);
				}
				if (status != RemoteRefUpdate.Status.OK && status != RemoteRefUpdate.Status.UP_TO_DATE)
					error = true;
			}
			// TODO: return results for all updated branches once push is available for remote, see bug 352202
		}
		// needs to handle multiple
		result.put("Severity", error ? "Error" : "Ok");
	} catch (JSONException e) {
	} finally {
		if (db != null) {
			db.close();
		}
	}
	return new ServerStatus(Status.OK_STATUS, HttpServletResponse.SC_OK, result);
}
 

public abstract GitTransportUpdate createTransportUpdate (URIish urI, TrackingRefUpdate update);