Resolve Conflicts with Simulink Three-Way Merge

This example shows you how to use Simulink® Three-Way Merge to resolve conflicts in Simulink models. You can view and merge the Simulink model differences in the resulting report.

Simulink Model Changes in This Example

This example shows you how to use Three-Way Merge to understand and resolve the differences between two conflicting Simulink design changes. The example Simulink project is under source control (Git in this example) and contains changes which conflict with another user's. You will use the Three-Way Model Merge tool to resolve the conflicts. You will examine your local file ("Mine"), the conflicting revision ("Theirs") and the common ancestor of these two files ("Base").

The conflict in this example was caused by the current user trying to merge the changes of another user on the master Git branch (the 'Theirs' changes) into their Task1 branch (containing the "Mine" changes).

Theirs: The pilot model subsystem was updated to use an explicit gain block for the amplitude of the pilot's input commands. The Simulation stop time was also updated.

Mine: The current user changed some configuration settings for the model.

The Merge tool automatically merges nonconflicted differences. Follow the steps below to review the automerge choices, edit if desired, and decide how to resolve any remaining differences. This will then allow you to commit the resolved model to source control.

Set Up Example Simulink Project

Run the following commands to create and open the project.


Open Simulink Three-Way Merge

Look for conflicted files in the Simulink Project files view. The slproject_f14 file shows a red warning symbol in the Git column, which indicates a conflict.

1. To see a detailed report of the conflicts, right-click the slproject_f14 file and select 'View Conflicts'.

View Changes

The Three-Way Merge tool shows the changes to the two Simulink designs that have caused this file conflict.

  • At the top, Theirs, Base and Mine trees show the differences between the conflicting revision, your revision, and the base ancestor of these files.

  • Underneath, the Target area shows the file that you will merge changes into. This is a temporary file and will be copied into the Simulink project when you choose to accept the merge result.

2. Examine a difference by clicking a row in one of the trees. The merge tool displays the change for each model in an editor, for example the Simulink Editor or Configuration Parameters dialog box, to the right of the Three-Way Merge window.

3. Choose the models to display with the toolstrip buttons on the Merge tab, in the Highlight section: Top Model or Bottom Model.

Review Automatic Merges

The merge tool automatically merges most nonconflicted differences.

4. Examine the first change at the top of the 'Theirs' tree by clicking the row called 'PilotGain'. This node has been merged automatically and you can adjust the automatic choices using the radio buttons in the target pane. If you want, review the other automatic merge choices.

Resolve Conflicts

There are two types of difference that require user action.

Conflict: The merge tool cannot automatically resolve these differences and you need to choose which design you want in the target file. Look for warnings in the Conflicts column.

Manual merge: Some differences must be merged manually in Simulink or ignored. In the Target pane, these items are indicated by an icon with a pencil in the Conflicts column.

5. Select the 'StickCommand_rad' row. This difference requires a manual merge, indicated by a pencil on the icon in the Conflicts column.

Resolve the line change difference in the target file by renaming the line connected to the output of the block named 'Pilot' in the Simulink Editor from 'StickCommand_rad' to 'Pilot Output'.

After resolving the difference save the changes in the Editor, and mark the change resolved using the manual merge control in the Conflicts column.

Note - the merge report does not update to show any changes you make in the Editor.

6. Use the 'Next' toolstrip button to review and resolve the changes until you reach a conflict. This StopTime parameter has been changed by both users and is conflicted. Resolve the conflict using the 'Mine' change. Select the 'Mine' radio button next to StopTime in the Target pane.

Change Filters

By default the report hides all nonfunctional changes, such as the repositioning of items.

7. Turn off filters using the Filters toolstrip section to explore all the differences between these designs.

Accept Changes

8. After you resolve all filtered and unfiltered changes, click 'Accept & Close'. The merge tool closes the report and the models, accepts the merge result in the target file, and marks the conflict as resolved in the source control tool (Git in this example). Resolved conflicts make it possible to commit changes to source control and continue your work.