javagit/src/main/java/edu/nyu/cs/javagit/client/cli/CliGitCheckout.java
public GitCheckoutResponse checkout(File repositoryPath, GitCheckoutOptions options, Ref branch,
                                        File path) throws JavaGitException, IOException {
        CheckUtilities.checkFileValidity(repositoryPath);
        GitCheckoutParser parser = new GitCheckoutParser();
        List<File> paths = new ArrayList<File>();
        paths.add(path);
        List<String> command = buildCommand(options, branch, paths);
        GitCheckoutResponse response = (GitCheckoutResponse) ProcessUtilities.runCommand(repositoryPath,
                command, parser);
        return response;
    }
public GitCheckoutResponse checkout(File repositoryPath, GitCheckoutOptions options, Ref branch,
                                        File path) throws JavaGitException, IOException {
        CheckUtilities.checkFileValidity(repositoryPath);
        GitCheckoutParser parser = new GitCheckoutParser();
        List<File> paths = new ArrayList<File>();
        paths.add(path);
        List<String> command = buildCommand(options, branch, paths);
        GitCheckoutResponse response = (GitCheckoutResponse) ProcessUtilities.runCommand(repositoryPath,
                command, parser);
        return response;
    }
Checks out a file from repository from a particular branch