Using Version Control in Studio Pro

Introduction

This document describes how to use version control in Mendix Studio Pro.

For more information on related concepts and the theory behind how version control works in Mendix, see Version Control.

Starting an App with Version Control

To start a new app with version control, do the following:

1. Open Studio Pro.
2. In the Select App dialog box, click Create New App.
3. Select the starting point – an app template.
4. In the App Settings dialog box, make sure that Enable online services is set to Yes. This option creates a remote (Team Server) repository and an app in Apps of the Mendix Portal.
5. Optionally, change the default App directory set by Studio Pro.
6. Click Create app.

The app is created on the Team Server, and a working copy is created in the App directory. This is opened in Studio Pro so that you can start working immediately.

Joining an App

If there is already a Team Server-enabled app, you can be invited to join it (see Team).

Once you are a team member, provided that you have been given a role with sufficient rights, you can work on the app by doing the following:

1. Choose Open App in Studio Pro.
2. Choose your app from the list of the Open App dialog box.
3. Click Open in Studio Pro.

The app will be downloaded from the Team Server and opened in Studio Pro.

Day-to-Day Development

Let us say you have a working copy of an app on disk. You make changes to the app and save them. Saved changes are not immediately visible to others. The documents, folders, and modules that have been changed can be identified by looking at the status.

When you are happy with a set of changes, you commit and push them to the remote repository (Team Server). Others can then choose to update/pull and retrieve those changes.

You can update/pull your working copy with changes committed by others.

You can also see a history of all the changes that have been committed, no matter who committed them.

Status

The status of your app is a summary of all the changes in your working copy when compared with the original (the original version is the version you pulled from the remote repository before making your changes (or the newly created app if you have not pulled anything yet). Studio Pro shows the status both in the App Explorer and in the Changes pane.

The App Explorer shows an icon in front of items (such as documents, folders, and modules) to present that are changed in some way. The different icons indicate the different kinds of changes which have been made.

Icon	Meaning
	Nothing happened to this item. It is unchanged with the respect to the original.
	You modified this item.
	You added this item.
	You moved this item to another position in the app tree.
	You deleted this item.
	You and somebody else made conflicting changes to this item. For more information, see the Dealing With Conflicts section below.

For example, the microflow ChangePassword has been modified. Also a new folder called Flows was added and all microflows, including the modified microflow, were moved into this folder. The new folder gets a green icon, and the module containing those changes is depicted with a yellow icon. The microflows which were moved but had not been modified get a blue icon. The modified microflow ChangePassword gets a yellow icon. This helps you to quickly see where in the app the changes are.

In the Changes pane, you can find more detailed information. There is an entry for each change to an item. If a document is both modified and moved, there are two lines for that document. The pane also shows items that were deleted, something the app explorer cannot do. For more information, see Changes Pane.

If you also changed Java source code, added widgets, or made other changes that affect files other than the app file, you will see entry for each changed file. You can right-click the entry and click Open containing folder to open the folder with the file on disk. For files with the Modified status, you can use Compare with original that opens an external tool to show the differences.

Committing

Sending changes to the local repository is called committing. The idea is that you commit small, consistent pieces of work to the repository. Mendix recommends committing your changes often. Preferably, the versions in the repository are always error-free. Studio Pro warns against committing while there are errors in your app.

To commit your changes, click the Commit button in the Changes pane, or choose the Version Control > Commit menu item.

Git only creates a local commit. To submit your local commit (or commits) to the remote repository, you need to push your changes to the remote repository. You can choose between committing and pushing right away or committing locally.

For example, you are developing a feature together with another developer on the same branch. You both have the same starting point (3). When your colleague commits a change, you can choose to retrieve these changes and integrate them. To enable this, developers first need to commit existing changes locally (6), so that the changes can be automatically merged when they are retrieved by other developers. After this, you commit the merged result, and optionally push the merged result (7) to be used by your colleague. Because changes are already explicitly committed, you can always see what you changed and you cannot accidentally override your local changes when you are resolving conflicts.

In general, it is a good idea to commit after implementing one feature or fixing one bug. By committing often, your work is integrated with the work of others regularly. The benefits of committing include the following:

• If any conflicts arise, the changes are still fresh in your mind
• Revisions are easier to understand
• If you ever need to revert something, you can revert a small chunk of work

Committing results in a new revision in the repository. You can add the following information in Studio Pro when you perform a commit, and this will be attached to the newly created revision:

• A textual message – this should be a summary of the changes you made.
• A list of stories that relate to the commit; for more information, see Stories Pane.

Studio Pro also attaches some information automatically:

• The person who committed (the Author)
• The date and time of the commit
• The list of changed documents, folders, and modules along with the type of the change (for example, modify or add)
• The version of Studio Pro that was used to commit

If you also changed Java source code, added widgets, or made other changes that affect files other than the app file, you will see a Changes on disk tab that shows you what disk changes you are about to commit. Open containing folder opens the folder with the file on disk. For files with the Modified status, you can use Compare with original that opens an external tool to show the differences.

Committing is only allowed if your working copy is up to date with the repository. If someone else committed a change since the last time you pulled, you will have to pull first. This is because the revision you create with the commit should incorporate both your changes and the changes by the other person. Updating will combine the latest changes in the repository with your changes. After reviewing the result and fixing any conflicts, you can commit again.

Pushing

Pushing is sending local commits from your local repository to the remote repository (Team Server). After committing, you need to push the committed changes if you want them to be accessible to others. By default, this is done when committing, but it is possible to wait for this step until later.

To push changes, select Version Control > Push or simply use the Commit and Push button in the Commit dialog box. In this case changes are pushed automatically when you commit them:

Push Fast-Forward Only

While you were working on your branch, somebody may have pushed their changes to the same branch on the server already. In this case, pushing is not possible and you will need to take further action first.

In Studio Pro, automatic fetching can be used to discover changes on the server. If at the moment when you click Commit Studio Pro knows that there are remote changes, the commit dialog will contain a note about this, and the Commit and Push button will be replaced by Commit and combine.

If the changes are discovered during the push, an information dialog with instructions is shown.

Git prevents you from pushing your changes if it sees your changes and the remote changes as potentially conflicting. In this diagram, you see that Git does not know how to combine commits #3 and #4.

There are two ways for Studio Pro to combine the commits: Rebase (default) and Merge. For more information, see Combining Changes and Conflict Resolution.

Pulling

Pulling retrieves the latest changes from the remote repository. You need to do this to incorporate any changes made by others that are not yet in your working copy before you can commit your changes to the repository. It is advisable to frequently update so that the number of changes you retrieve is small.

To update the working copy of your app, click Pull in the Changes pane, or choose the Version Control > Pull menu item.

Changes you receive from the remote repository when pulling are combined with the changes you have made to your working copy (if any). Afterwards, your working copy will contain both your changes and the changes you received. As part of the pull, the original of your working copy is updated as well.

For example, if the last time you pulled you received all changes up to and including revision N, this means that the original for your working copy is revision N. Since you started making changes to your working copy, other people on your team have made another three commits (X, Y, and Z). If you now pull, you will receive those changes and Z will be the new original to which your changes are compared.

Usually, combining your changes with the latest revision from the repository is done automatically. For example, one person may add a page while you are changing a microflow. If the changes are too close, however, a conflict can arise. For example, if one of your team has changed the properties of the same data view that you have also changed, you will have to resolve such conflicts before you can commit. For information on how to do this, see Combining Changes and Conflict Resolution.

If your team is committing often, you then should pull often. Frequent pulling has the benefit that you receive fewer changes with each pull so that integrating those changes with your work is easier.

History

The history of the app is a list of all revisions that have been committed. To view the history of the app, click the History button in the Changes pane, or choose the Version Control > History menu item.

For Git-based applications, revisions are sorted according to the commit history, which sometimes does not reflect the chronological order due to Git’s decentralized nature and local commits. The history dialog shows you revision number, date, time, author, and message of each revision.

Select a revision to see additional details, such as related stories, changed documents, Studio Pro version, and changes on disk. Icons summarize the kinds of changes that happened in the app.

Reverting Changes

Changes that have not yet been committed can be reverted. Say, for example, that you have made a lot of changes to a page and you are not happy with the result. You can revert the page to the original state, that is, the state of the page before you started making changes.

Deletes of documents, folders, and modules can also be reverted. This brings them back into the app. Note that you will get back the latest version you have committed. For example, if you commit, make some changes to a microflow, and then delete the microflow, reverting the delete gives you the microflow without the changes that you made.

You can revert changes in the Changes pane, from Version Control > Revert All Changes, or from the right-click menu on the document you want to revert.

Dealing With Conflicts

If you update/pull your app and the changes cannot be merged automatically, you will receive a message telling you that there are conflicts. A conflict arises when two changes cannot be combined.

For more information, see Combining Changes and Conflict Resolution.

Using Branches

A repository (remote or local) can contain a number of development lines. Each development line offers independent development from the other development lines. In the simple case there is just one development line called the main line. All development then happens inside that one line.

It is often convenient to have more than one development line. For example, one development line is for fixing bugs in the currently deployed version of your app and another line is where you develop new functionality. If you then find a bug in the deployed version, you can fix it in the corresponding development line irrespective of the state of the development line where new functionality is developed. For more information about branches, see the Branches section in Version Control.

Working with Branches in Studio Pro

This section outlines how to create branches in Studio Pro. It also recommends some Branching Best-Practices when developing Mendix apps.

Branching

Development lines other than the main line are called branch lines. You can consider developing new features in the main line and using branch lines for fixing bugs in versions that have been deployed. This is the scenario Studio Pro makes easy but other scenarios for more complex apps are supported as well.

You can create branch lines from the Branch Line Manager which you can find at Version Control > Manage Branch Lines….

The most common examples on using branch lines are patching a deployed application and developing a new feature.

Patching a Deployed Application

If you want to add some functionality to a deployed application or you want to fix a bug in it, you can do so without interfering with other development.

1. Determine the version of the deployed application. This information is in the Mendix Portal. Alternatively, you can find the version in the metadata.json file in the model subfolder of your deployment package (mda) archive, for example, "ModelVersion": "1.0.0.16".

2. Choose Version Control > Manage Branch Lines… and create a branch based on the tag with the version number as its name.

   

3. Add the functionality or fix the bug in this newly created branch.

4. Testing that things work as intended.

5. Create a new deployment archive with a higher version number (increase patch or minor version).

Developing a New Feature Independently

Another reason for creating a branch is to develop a big new feature without interfering with other development. This gives you the freedom to commit a half-implemented feature, possibly even with errors, while other people can still commit and update/pull on the main line. Without using a branch line, you would have to constantly make sure that your app is error free and does not break other parts of the system.

Firstly, select Version Control > Manage Branch Lines… and create a branch from a revision of the main line.

Now work on the branch until the feature is done, commit the completed work and merge your branch back to the main line (for more information on merging, see the Merging section below).

You can delete the branch after merging it back, if you want.

Merging

If you have multiple development lines, you sometimes want to merge changes from one development line to another. For example, the fix that you made in a branch line for the production version should also be applied to the new 2.0 version you are developing in the main line. You can, of course, do this by hand but Studio Pro can also help you by merging changes from one development line to another.

Merging is always done while you have a working copy open. The merge will result in extra local changes in that working copy. It is advisable to commit local changes first before merging extra changes into a working copy. Otherwise, the uncommitted local changes and the changes caused by the merge will be combined and it is very hard to untangle them if you are unhappy with the merge. Studio Pro will warn you if you have uncommitted changes.

Select Version Control > Merge Changes Here, after that you can select Port fix or Merge feature branch options. For more information on merge settings, see Merge Dialog.

Reverting a Commit

Reverting changes works for changes that have not been committed yet. Changes that have been committed and pushed to the server can never be deleted from the history. However, you can make another commit to revert the changes. This feature is called Reverse commit in Studio Pro.

Choose the Version Control menu > Revert a Commit… to revert a commit.

Reverting changes is done with one commit at a time. If you want to revert multiple commits, you can do that by reverting the latest commit, then the previous one, only one by one.

After a reverse merge the app will look like the changes never happened; if you reverse merge adding a new page, the page will be deleted locally. Just like when you are doing a normal merge, conflicts can arise. For example, if later commits change the new page, the reverse merge will result in a conflict. After resolving the conflict, you can commit and push the results to the remote repository.

Replacing the Main Line with a Branch Line

There are two methods for fully replacing your main line with a branch line.

The first method is to merge the entire branch line into the main line, essentially replacing the main line contents with the branch line contents. This works as long as the branch line is up to date with the main line (to avoid conflicts). To do this, follow these steps:

1. Select Version Control > Merge Changes Here > Merge feature branch.
2. Select the branch to merge into the main line.

The second method should be used if the first method is not possible for some reason and you want to “overwrite” the main line with your branch line. To use the second method, follow these steps:

1. Check out both the main line and the branch line locally.
2. Overwrite all the files in the main line app directory with those of the branch line (except for the .git directory).
3. Commit your changes using Studio Pro.
4. Reopen the main line app in Studio Pro only after overwriting the files.

Merging Using Git in the Command Line

For merging .mpr files using Git in the command line to work, it is necessary to attach mx.exe merge to Git as a driver.

When doing a git merge operation on two branches in the command line, Git attempts to merge the binaries of .mpr files, which does not work. You need to apply Studio Pro merge algorithm and that is where mx.exe as a driver is needed.

Navigate to the .gitconfig file in C:/Users/[USER_NAME] and add the following:

[core]
  attributesfile = ~/.gitattributes
[merge "custom"]
  name = custom merge driver for specific files
  driver = [MX.EXE_PATH] merge %O %A %B

[MX.EXE_PATH] should be replaced by the mx.exe path with only forward slashes pointing to a drive using /C/ instead of C:/.

You can also configure the Git driver locally per repository using the following commands:

git config merge.custom.name "custom merge driver for specific files"
git config merge.custom.driver "[MX.EXE_PATH] merge %O %A %B"

After setting up the driver either locally or globally, create a .gitattributes file in the same folder with the following contents:

*.mpr merge=custom

Save the files and now when git merge is run and it involves .mpr files, the mx.exe merge will run Studio Pro merge algorithm before Git finishes the merge.

Branching Best-Practices

Depending on your team’s size and preferences, you may find some branching strategies better suited than others. Mendix suggests using one of the following three strategies which have increasing complexity and control and different pros and cons.

• Trunk-Based (Single Branch Line): straightforward, easy to start with, well-suited for small teams
• Trunk-Based with Feature Branches: reduces risk of merge conflicts, well-suited for larger teams and a regular release cadence
• Advanced Branching: guarding quality becomes easier, well-suited for large teams and structured processes

We recommend starting trunk-based and adopting trunk-based with feature branches next, if needed. Getting a lot of merge conflicts or releasing a first version to production are sensible triggers to move away from solely trunk-based development.

For experienced teams, or for organizations with stricter processes and/or auditability criteria, the advanced branching approach is recommended.

In the tips and tricks section you will find suggestions on how to work with, and manage, branches in an effective way.

Trunk-Based (Single Branch Line)

In trunk-based development, all developers work on a single branch, typically the “trunk” or “main” branch. Changes are frequently committed to this branch, and developers continuously push their work to the remote repository.

Benefits are:

• Simplicity: Trunk-based development is straightforward and easy to understand, making it suitable for small teams or projects with less complex requirements.
• Fast feedback: Developers receive immediate feedback on the impact of their changes, helping to identify and resolve issues quickly.
• Reduced merge conflicts: Since developers frequently push their code, the chances of encountering significant merge conflicts are minimized.

Disadvantages are:

• Risk of instability: Constant changes to the main branch can introduce instability, especially if proper testing and quality assurance practices are not in place.
• Limited parallel development: The single branch model can limit parallel development efforts, making it challenging to work on multiple features concurrently.
• Difficulty to mitigate issues: When encountering issues on production, it is not possible to deploy a hotfix without also publishing other changes to your app, without creating a branch.

This approach is best-suited for small teams.

Trunk-Based with Feature Branches

Trunk-based can also be combined with short-lived feature branches. Developers work on feature branches, which are created from the main branch. Once a feature is complete, it is merged back into the main branch.

Benefits are:

• Limited complexity: This approach is still relatively straightforward and easy to understand for most developers.
• Isolation of changes: Working on feature branches allows developers to isolate their changes, reducing the risk of disrupting the mainline codebase.

Disadvantages are:

• Overhead: Separate feature branches can lead to overhead in terms of merging, code review, and testing.

This approach is the most-used among Mendix customers, and is best-suited for teams with some experience, or teams running into the limitations of trunk-based development.

Advanced Branching

In branch-based development, there are typically two types of branches:

• Long-lived branches: main branch, development branch, release branch
• Short-lived branches: feature branches

Developers work on feature branches, which are merged into the development branch for integration and testing. The release branch is used to prepare for a stable release, while the main branch represents the production-ready codebase.

Benefits are:

• Isolation of changes: Working on feature branches allows developers to isolate their changes, reducing the risk of disrupting the mainline codebase.
• Parallel development: Multiple features can be developed simultaneously, enhancing productivity.
• Granular control: Different branches provide granular control over the development and release process.
• Stability and quality: The main and release branches are stable and thoroughly tested, ensuring high-quality releases.
• Scalability: This strategy scales well with larger teams and complex projects

Disadvantages are:

• Complexity: Managing multiple long-lived branches and their interactions requires careful planning and coordination.
• Overhead: Maintaining separate branches can lead to overhead in terms of merging, code review, and testing.

This approach is best-suited to large teams or teams preferring a more rigid process. Projects with strict release cycles can also benefit from this approach, as the release branch is always stable.

Tips and Tricks for Working with Branches

There are several recommendations that make it easier to work with and manage multiple branches.

• Periodically merge higher-level branches, such as ‘development’ or ‘main’, to lower-level branches, such as feature branches. This ensures you already take the most recent stable work into account when developing a feature, preventing larger merge conflicts down the road.
• Note which branch is being used for development in the stories that you are working on, to avoid confusion. You can also implement a naming convention for branch names, such as feature_[issueNumber].
• Where possible, keep different branches on the same version of Studio Pro.
• Make sure that old branches are cleaned up, to prevent accumulating them over time. Ideally you should delete a branch as part of the process of completing a feature. In cases where branches aren’t merged in the end, consider cleaning them up periodically.

Versioning an App Deployed to the Cloud

Deploying Locally

While developing, you can deploy and run your app on your local machine by clicking the menu item Run > Run Locally. This allows you to test the app as it currently is stored on your local machine.

Deploying Your Working Copy

When you deploy to the cloud, you can choose to use the version of the app stored on your local machine, the working copy and deploy that to the default environment. If you are using the Mendix Cloud, or other partner cloud (SAP BTP, for example), click Publish to commit and push the version of the app stored on your local machine and deploy that to the default environment.

Choosing a Specific Development Line and Revision

It is also possible to choose a specific development line and revision to deploy to the default environment, or to create a package from.

In this case, Studio Pro will create a fresh checkout of the chosen revision. This means that any team member can always recreate this version of the deployment package. In other words, Studio Pro does not rely on your local files for creating a versioned deployment package.

When it creates the package, Studio Pro will also create a tag representing this version of your app. If you want to make modifications to this version later, independently of other development which has taken place, you can create a branch based on this tag. The name of the tag is a version number that you choose.

Deploying a Specific Version to a Mendix Licensed Cloud Node

If you are using Mendix Cloud, you can choose App > Deploy to Licensed Cloud Node to deploy a specific version.

Creating a Deployment Package from a Specific Version

If you are using a different hosting environment, you create a deployment package using the menu item App > Create Deployment Package.

Working Outside Studio Pro

Studio Pro takes care of some file management automatically. If you add or remove custom widgets, they are automatically added or removed from version control too. Some files and directories (for example, deployment and releases directories) are automatically ignored so that they are not committed to version control.

We advise you to always commit and update/pull inside Studio Pro, because, in this way, useful metadata is added to your revisions. Studio Pro has ways to recover from external updates or merges but it is best to not depend on that.

External Tools

If you are doing more advanced changes to files, like adding Java actions or resources to your app, you will have to install a separate tool on your computer and perform some operations yourself: you can use TortoiseGit (can be downloaded for free).

Authenticating to Team Server

When using external tools, you might be asked to authenticate separately to Team Server.

Connecting to Git is done using a personal access token (PAT). For more information on how to create a PAT, see the Personal Access Tokens section of Mendix Profile.

To connect to Git, you need to use the following URL and credentials:

• URL: https://git.api.mendix.com/<your AppID>.git
• Username: your Mendix account username (alternatively, you can use the word pat as your username)
• Password: the PAT you created – the PAT must include the scopes mx:modelrepository:repo:write, mx:modelrepository:repo:read, and/or mx:modelrepository:write under Model Repository

Adding and Deleting Files and Directories

If you add or delete files (or directories) using Windows Explorer, Studio Pro automatically adds or deletes these from version control too. A folder is no longer tracked if all the files in the folder are removed.

Make sure you use the Export feature of TortoiseGit if you are copying a directory that is already under version control in your app.

Branching and Deploying

If you perform branching outside of Studio Pro, you will not be able to immediately deploy to Mendix Cloud. That is because Studio Pro adds metadata about the Mendix version of your app to each revision when you commit or create a branch, which is needed by the Mendix Cloud deployment. Branching outside of Studio Pro means that metadata is missing from your branch, thus your app cannot successfully be deployed.

To fix this, make a small commit on your branch in Studio Pro (for example, changing a documentation field). Studio Pro will then add the metadata that Mendix Cloud deployment requires, and you will be able to deploy your app.

Reverting Accidental Studio Pro App Model Upgrade

When working in different apps with different Studio Pro versions, you may one day find yourself with an app model upgraded and committed to a newer Studio Pro version, while the rest of your team is not yet ready to upgrade.

To revert this version upgrade of the app model, use the Git tool of your preference to revert the change.

Integrating Git in a Build Pipeline

When building deployment packages in a pipeline outside the Mendix platform, you will need to retrieve a specific commit from the Git server. To avoid downloading the full repository every time you can use a clone with limited depth (shallow clone). With a minimal amount of data to retrieve, the operation is a lot faster and takes less toll on the version control server.

You can use the commands below to download a shallow clone. Note that they should only be used to download a single revision, as Studio Pro is not compatible with working on a shallow clone.

# make a new blank repository in the current directory
git init

# add a remote
git remote add origin url://to/source/repository

# fetch a commit (or branch or tag) of interest with limited history
git fetch --depth 1 origin <sha1-of-commit-of-interest>

# reset this repository's master branch to the commit of interest
git reset --hard FETCH_HEAD

Read More

• Advanced Branching and Merging Strategies