The MMT Language and System


This document explains the general development model of MMT. Before contributing to MMT, you should read this document to understand what is going on.

Coding Style

See here for some code conventions.


Main Branches

There are three central branches:

  • master: main development line, used by developers, stable and including latest features
  • release: used by external users, very stable, occasionally merged into from master
  • devel: a branch of master that is periodically merged into master; this branch is under constant development by Florian

Every MMT archive on MathHub has two corresponding branches master and release. For testing purposes, release branches of archives are tested against the release branch of MMT, and accordingly for master branches.

Feature Branches

MMT developers typically branch for individual features from master but may sometimes have to branch from devel. Usually this involves a discussion with Florian. In particular, inexperienced contributors and developers of cutting-edge features typically have to work with devel in order to collaborate with Florian.

MMT developers merge their features into devel or master according to their own judgment. Usually this involves an informal discussion with core developers or a pull request. If they merge into master, they must also merge the resulting master into devel.

Protections and Tests

Pushes to release must pass the corresponding test(s).

Pushes to master should pass the corresponding test(s). (This ‘should’ will probably become a ‘must’ in the future.)

All three main branches are protected from force-pushes.

The sbt build file contains the following tests:

  • release/build and release/test: build certain projects and certain archives that must work in releases
  • master/build and master/test: build certain projects and certain archives that should work on the master branch

Git workflows

Making changes in MMT is possible in two different ways, through making forks and making branches. Usually you should only contribute directly to a branch if you know what you are doing.

One way of making changes is to make a fork of the repository and then create a pull request to merge the changes back into the master branch. A fork is a copy of the repository that can be used to make a changes without affecting the original code. Pull requests should only be made after the actual code compiles and should always go onto the master branch.


External contributors are welcome to create forks. However, note that the MMT license forbids distributing forked versions. Therefore, forks are only useful if they are temporary. All changes in a fork should be reintegrated with the main project as fast as possible.

Students in the MMT research group(s) should never work on a fork. Exceptions are only allowed with their advisor’s permission. Instead, they should ask for a branch to be created for them.

Updating the release branch

To mark a version of MMT as a release, we again use pull requests. This time we merge from master onto release. Again go to the main repository page and select New pull request. Choose release as the base and master as the head. Now write a title as well as a description of the changes that have been made since the last merge to the release branch. Then create the pull request by clicking the “Create pull request” button.

Only repository owners and administrators can merge this pull request.

Once the travis tests have passed, the pull request can be merged by any core developer.

Sources and Useful reading

In general GitHub documentation is very helpful for any general questions:

Furthermore parts of this README have been adapted from