xPDO GitHub Contributor's Guide

Last edited by JP DeVries on Jul 19, 2013.

Contributing to xPDO and Integrating with MODX Revolution

xPDO is an object-oriented framework on which MODX Revolution is built. It is maintained in a separate git repository from revolution and contributing to the xPDO core of MODX requires some additional work.

xPDO contributors should follow the same basic process and branching strategy as those for MODX itself. See the MODx GitHub Contributor's Guide for details on the branching strategies for features, releases, hotfixes, and more. This guide will focus on the additional steps required to integrate your xPDO changes into MODX for testing before submitting Pull Requests on the xPDO repository.

Forking and Cloning the Complete xPDO Repository

As with MODX, this means contributors must work directly with their private forks on GitHub. Here is the suggested way to prepare your local repository as a developer for contributing back to the complete xPDO project:

[repos]$ git clone git@github.com:YourGitUsername/xpdo.git
[repos]$ cd xpdo
[xpdo]$ git remote add upstream -f http://github.com/modxcms/xpdo.git

This setup makes your fork the standard origin remote, and adds/fetches the "blessed" repository as the remote upstream. You may want to add other remotes to other developer forks as well, and I would name those remotes appropriately so you can keep track of each one.

You'll want to go ahead and create local tracking branches for the permanent branches from your fork, a.k.a. origin:

[xpdo]$ git checkout -b master origin/master
Switched to a new branch "master"
[xpdo]$ git checkout -b develop origin/develop
Switched to a new branch "develop"

To keep your local tracking branches for develop and master up-to-date from the upstream repository:

[xpdo]$ git fetch upstream
[xpdo]$ git checkout develop
Switched to branch "develop"
[xpdo]$ git merge --ff-only upstream/develop
[xpdo]$ git checkout master
Switched to branch "master"
[xpdo]$ git merge --ff-only upstream/master
[xpdo]$ git push origin develop master

Note however, that the push is mainly for show, as the permanent branches should never be a target for contributor commits, even in the forks. IOW, develop and master in your fork should always match the upstream branches of the same name. It is expected that all contributions will be submitted via a feature or hotfix branch originating from the appropriate permanent branch, or a bug fix branch originating from a release branch in the upstream repository.

Also note the --ff-only flag ensures that only fast-forward merges are performed (in case you accidentally do commit to the main branches on your fork without realizing it).

Please make sure you have your autocrlf settings set appropriately before making any commits to your fork. See http://help.github.com/dealing-with-lineendings/ to determine the setting you need based on the platform you are developing on.
Unit Tests
xPDO has a growing number of Unit Tests which help ensure at least basic functionality is not broken when changes are made to the code base. Make sure your changes pass the unit tests for ALL implemented drivers when submitting any Pull Requests to, or that affect, xPDO code. In addition, all bug fixes and features should be accompanied with new unit test cases where practical.

Forking and Cloning the xPDO Core Repository

xPDO has two GitHub repositories. The complete repository contains Unit Tests, test models, build scripts and other assets that you would not want integrated into other projects. In order to more easily merge the project within other projects, a second repository that includes only the xpdo/ subdirectory (this contains the run-time files of xPDO only) was created. This repository is kept in sync with the complete xPDO repository via git's subtree merge technique, and this same technique can then be used to merge the xPDO Core with any other git repository.

So the next step is to fork and clone this repository as well:

[repos]$ git clone git@github.com:YourGitUsername/xpdo-core.git
[repos]$ cd xpdo-core
[xpdo-core]$ git remote add upstream -f http://github.com/modxcms/xpdo-core.git

Migrating Changes for Testing

Whenever you have completed a feature or bugfix in the complete xPDO repository, all the unit tests are passing, and you are ready to test the change in another project, you can push the change to an appropriate branch on your fork. Once there, you can choose to manually copy your modified files into place in any external project you are using xPDO with, or use git's subtree merge technique to update the xpdo-core repository with your changes, and then turn around and do the same from xpdo-core into your project's repository.

To update the xpdo-core repository, we first need to add and fetch a remote for your fork of the complete xpdo repository:

[xpdo-core]$ git remote add -f xpdo git@github.com:YourGitUsername/xpdo.git

Once added, you can fetch changes you commit to your xpdo fork and merge them easily. Make sure your xpdo-core branches are up-to-date from upstream first, e.g. if pushing a feature branch called xpdo/feature-1234 off of the upstream/develop branch:

[xpdo-core]$ git fetch upstream
[xpdo-core]$ git checkout develop
Switched to branch "develop"
[xpdo-core]$ git merge --ff-only upstream/develop
[xpdo-core]$ git push origin develop
[xpdo-core]$ git fetch xpdo
[xpdo-core]$ git checkout -b feature-1234 develop
[xpdo-core]$ git merge -s subtree --log xpdo/feature-1234
[xpdo-core]$ git push origin feature-1234

At this point, your feature branch is in your xpdo-core fork and ready for merging into MODX Revolution or any other project that has xpdo-core subtree merged into it.

Testing Changes in MODX Revolution

Now, to test your changes with MODX Revolution, you need to add and fetch your fork of the xpdo-core repository as a remote to your revolution fork. Once you do that, you can create a branch to merge in and test your xpdo-core feature branch. Change directory to your MODX Revolution git fork and get it up-to-date.

[revolution]$ git checkout develop
Switched to branch "develop"
[revolution]$ git fetch upstream
[revolution]$ git merge --ff-only upstream/develop
[revolution]$ git push origin develop
[revolution]$ git remote add -f xpdo git@github.com:YourGitUsername/xpdo-core.git
[revolution]$ git checkout -b xpdo-feature-1234 develop
[revolution]$ git merge -s subtree --log xpdo/feature-1234

If it works, share your branch with the xpdo-core changes integrated with the world to play with:

[revolution]$ git push origin xpdo-feature-1234

Submitting the Pull Request

After all of this is done, and you are confident your changes should make it into xPDO, all you need to do is submit your original feature branch, on your fork of the complete xpdo repository, to the appropriate branch of the upstream xpdo repository.

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