public class GitClient implements IGitClient{
	
	private String remoteRepositoryUI;
	private String localRepositoryPath;
	private Git localGit;
	private UsernamePasswordCredentialsProvider credentialsProvider;
	
	public GitClient(String remoteRepositoryURI, String localRepositoryPath, 
			String user, String password) {
		this.credentialsProvider = new UsernamePasswordCredentialsProvider(user, password);
		this.remoteRepositoryUI = remoteRepositoryURI;
		this.localRepositoryPath = localRepositoryPath; 
	}
	
	public void addFile(String sourceFilePath, String repositoryFilePath, Branch branch, String message) throws Exception {
		if(!isInitialized())
			initialize(branch);	
		switchBranch(branch);
		FileUtils.copyFile(new File(sourceFilePath), 
				new File(this.localRepositoryPath + File.separator + repositoryFilePath));
		localGit.add().addFilepattern(repositoryFilePath).call();
	    localGit.commit().setMessage(message).call();
	    localGit.push().setCredentialsProvider(this.credentialsProvider).call();
	}

	public File getFile(String repositoryFilePath, Branch branch) throws Exception {
		if(!isInitialized())
			initialize(branch);
		switchBranch(branch);
		localGit.fetch().call(); //<-- Problematic part
		//localGit.pull().call();
		return new File(this.localRepositoryPath + File.separator + repositoryFilePath);
	}

	private void switchBranch(Branch branch) throws InvalidRemoteException, TransportException, IOException, GitAPIException {
		if(!isInitialized())
			initialize(branch);
	    localGit.checkout()
	    	.setName(branch.toString())
		    .setUpstreamMode(SetupUpstreamMode.TRACK)
		    .setStartPoint("origin/" + branch.toString()).setForce(true)
		    .call();
	}

	private boolean isInitialized() {
		return this.localGit != null;
	}

	private void initialize(Branch branch) throws IOException, 
				InvalidRemoteException, TransportException, GitAPIException {
		File localRepositoryDirectory = new File(this.localRepositoryPath);
		boolean localRepositoryExists = localRepositoryDirectory.exists() && localRepositoryDirectory.isDirectory() && localRepositoryDirectory.listFiles().length != 0;
		
		if(!localRepositoryExists) {
			Git.cloneRepository()
			.setCloneAllBranches(true)
			.setBranch("refs/heads/" + branch.toString())
			.setURI(this.remoteRepositoryUI)
			.setDirectory(new File(this.localRepositoryPath))
			.call();
		}
		
		this.localGit = Git.open(new File(this.localRepositoryPath));            
		
		if(!localRepositoryExists) {
			for(Branch aBranch : Branch.values()) {
				if(!branch.equals(aBranch)) {
					localGit.checkout().setCreateBranch(true)
				    .setName(aBranch.toString())
				    .setUpstreamMode(SetupUpstreamMode.TRACK)
				    .setStartPoint("origin/" + aBranch.toString())
				    .call();
				}
			}
		}
	}
	
	public static void main(String[] args) throws Exception {
		GitClient clientA = new GitClient("URLToRepository.git",
				"local", "username", "password");
		GitClient clientB = new GitClient("URLToRepository.git",
				"localB", "username", "password");
		
		clientA.addFile("fileA1", "fileA1", Branch.master, "clientA1");
		clientB.addFile("fileB1", "fileB1", Branch.master, "clientB1");
		clientB.addFile("fileB2", "fileB2", Branch.development, "clientB2");
		clientA.addFile("fileA2", "fileA2", Branch.development, "clientA2");
		clientA.addFile("fileA3", "fileA3", Branch.master, "clientA3");
		
		File file = clientA.getFile("fileA1", Branch.master);
		System.out.println(file.getAbsolutePath() + " " + file.exists());
		
		file = clientA.getFile("fileA2", Branch.development);
		System.out.println(file.getAbsolutePath() + " " + file.exists());
		
		file = clientA.getFile("fileA3", Branch.master);
		System.out.println(file.getAbsolutePath() + " " + file.exists());
		
		file = clientA.getFile("fileB1", Branch.master);
		System.out.println(file.getAbsolutePath() + " " + file.exists());
		
		file = clientA.getFile("fileB2", Branch.development);
		System.out.println(file.getAbsolutePath() + " " + file.exists());
	}
	
}

[core]
	repositoryformatversion = 0
	filemode = false
	logallrefupdates = true
[remote "origin"]
	url = URLToRepository.git
	fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
	remote = origin
	merge = refs/heads/master