MakeCode allows to package and share code as Extensions. Extensions are stored as GitHub repositories and can be edited directly from the MakeCode editor.

Account setup

First, you need a GitHub account if you don't have one yet. GitHub is the largest host of source code in the world, with over 30 million users.

Once you have your account, you'll need to tie the MakeCode web app to your account. To do that, open any project in https://maker.makecode.com, go to the Gear Wheel menu on top, and select Extensions. At the bottom, there should be a link to log in to GitHub. A dialog will appear asking you to generate a GitHub token. Follow the instructions and paste the token into the dialog.

Once you've logged in, go back to the home screen. Now, the dialog that comes up after you press the Import button will have an additional option to list your GitHub repositories or create a new one.
Additionally, the Import URL option will now support https://github.com/... URLs, which is useful if you can't find your repository in the list (especially organizational repos), or as way to search the list faster using a copy/paste of the URL.

If you import a completely empty repo, or create a fresh one, MakeCode will automatically initialize it with pxt.json and other supporting files. If you import a non-empty repo without the pxt.json file, you will be asked if you want it initialized. Note that this might overwrite your existing files.

Commit and push

Once you have your repo set up, edit files as usual. Whenever you get to a stable state, or just every now and
then to keep history and insure against losing your work, push the changes to GitHub. This is done with a little GitHub sync button on top of the Explorer. The button will check if there are any pending changes to check in. If there are, it will create a commit, pull the latest changes from GitHub, merge or fast-forward the commit if needed, and push the results to GitHub.

If there are changes, you will be asked for a commit message. Try to write something meaningful, like
Fixed temperature reading in sub-freezing conditions or Added mysensor.readTemperature() function.

When describing changes, you are also given an option to bump the version number. This is a signal that the version you're pushing is stable and the users should upgrade to it. When your package is first referenced, the latest bumped version is used. Similarly, if there is a newer bumped version, a little upgrade button will appear next to the package. Commits without bump are generally not accessible to most users, so they are mostly for you to keep track of things.

We do not really distinguish between a commit, push, and pull - it all happens at once in the sync operation.

You can view a history of changes by following the version number link on the Project Settings page.

There is also another button next to the GitHub sync - you can use it to add new files to the project.
This is mostly to help keep the project organized. For our TypeScript compiler it doesn't matter if you
use one big file or a bunch of smaller ones.

Conflicts

It's possible that multiple people are editing the same package at the same time causing edit conflicts. This is similar to the situation where the same person edits the package using several computers, browsers, or web sites. In the conflict description below, for simplicity, we'll just concentrate on the case of multiple people working on the same package.

Typically, two people would sync a GitHub package at the same version, and then they both edit it. The first person pushes the changes successfully. When MakeCode tries to push the changes from the second person,
it will notice that these are changes against a non-current version. It will create a commit based on the previous version and try to use the standard git merge (run server-side by GitHub). This usually succeeds if the two people edited different files, or at least different parts of the file - you end up with both sets of changes logically combined. There is no user interaction required in that case.

If the automatic merge fails, MakeCode will create a new branch, push the commit there, and then create a pull request (PR) on GitHub. The dialog that appears after this happens will let you go to the GitHub web site and resolve the conflicts. Before you resolve conflicts and merge the PR, the master branch will not have your changes (it will have changes from the other person, who managed to commit first). After creating the PR, MakeCode moves your local version to the master branch (without your changes), but don't despair they are not lost! Just resolve the conflict in GitHub and sync to get all changes back. MakeCode will also sync automatically when you close the PR dialog (presumably, after you resolved the conflict in another tab).

Testing your package

To test blocks in your package, press the New Project button on the home screen and go to the Extensions dialog. It will list all your GitHub projects as available for addition. Select your package and see what the blocks look like.

You can have one browser tab open with that test project, and another one with the package. When you switch between them, they reload automatically.

For testing TypeScript APIs you don't need a separate project, and instead can
use the test.ts file in the package itself. It is only used when you run the package
directly, not when you add it to a project. You can put TypeScript test code in there.