Code for blog post: How to automatically push every change to an external repository

GitHook.java

public class GitHook {

    public static void main(String[] args) throws IOException, GitAPIException {
        // collect the repository location <1>
        final Path currentPath = new File("").toPath().toAbsolutePath();
        final String parentFolderName = currentPath.getParent().getName(currentPath.getParent().getNameCount() - 1).toString();
        // ignoring system space <2>
        if (parentFolderName.equalsIgnoreCase("system")) {
            return;
        }

        // setup GitHub credentials and integration  <3>
        final GitHubCredentials ghCredentials = new GitHubCredentials();
        final GitHubIntegration integration = new GitHubIntegration();

        // setup the JGit repository access  <4>
        final Repository repo = new FileRepositoryBuilder()
                .setGitDir(currentPath.toFile())
                .build();
        final Git git = new Git(repo);

        // collect all remotes for the current repository  <5>
        final StoredConfig storedConfig = repo.getConfig();
        final Set<String> remotes = storedConfig.getSubsections("remote");
        if (remotes.isEmpty()) {
           //create a remote repository, if it does not exist <6>
            new SetupRemote(ghCredentials, integration).execute(git, currentPath);
        }

        // mechanism to find the latest commit <7>
        final List<Ref> branches = git.branchList().setListMode(ListBranchCommand.ListMode.ALL).call();
        final RevWalk revWalk = new RevWalk(git.getRepository()); <8>

        branches.stream()
                .map(branch -> {
                    try {
                        return revWalk.parseCommit(branch.getObjectId());
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                })
                .max(comparing((RevCommit commit) -> commit.getAuthorIdent().getWhen()))
                .ifPresent(latestCommit -> {
                // the integration here <9>
                });
    }
}

integration-code.java

//get the branches where this commit is referenced <1>
final Map<ObjectId, String> branchesAffected = git
        .nameRev()
        .addPrefix("refs/heads")
        .add(latestCommit)
        .call();

//iterate over all remote repositories <2>
for (String remoteName : remotes) {
    final String remoteURL = storedConfig.getString("remote", remoteName, "url");
    for (String ref : branchesAffected.values()) { <3>
        // push changes to the remote repository <4>
        git.push()
                .setRefSpecs(new RefSpec(ref + ":" + ref))
                .setRemote(remoteURL)
                .setCredentialsProvider(ghCredentials.getCredentials())
                .call();

        //check if the branch has a remote config <5>
        final String remote = storedConfig.getString("branch", ref, "remote");
        if (remote == null) {
            //branch had no remote info, now needs to be update  <6>
            storedConfig.setString("branch", ref, "remote", remoteName);
            storedConfig.setString("branch", ref, "merge", "refs/heads/" + ref);
            storedConfig.save();
        }
    }
}

post-commit.sh

#!/bin/bash
java -jar $APP_SERVER_HOME/hooks/git-push-1.0-SNAPSHOT.jar // <1>