how to fix merge conflicts

Merge request conflict resolution

Merge conflicts occur when two branches have different changes that cannot be merged automatically.

Git is able to automatically merge changes between branches in most cases, but there are situations where Git will require your assistance to resolve the conflicts manually. Typically, this is necessary when people change the same parts of the same files.

GitLab will prevent merge requests from being merged until all conflicts are resolved. Conflicts can be resolved locally, or in many cases within GitLab (see conflicts available for resolution for information on when this is available).

Merge request widget

NOTE: Note: GitLab resolves conflicts by creating a merge commit in the source branch that is not automatically merged into the target branch. This allows the merge commit to be reviewed and tested before the changes are merged, preventing unintended changes entering the target branch without review or breaking the build.

Resolve conflicts: interactive mode

Introduced in GitLab 8.11.

Clicking this will show a list of files with conflicts, with conflict sections highlighted:

Conflict section

Once all conflicts have been marked as using 'ours' or 'theirs', the conflict can be resolved. This will perform a merge of the target branch of the merge request into the source branch, resolving the conflicts using the options chosen. If the source branch is feature and the target branch is master, this is similar to performing git checkout feature; git merge master locally.

Resolve conflicts: inline editor

Introduced in GitLab 8.13.

The merge conflict resolution editor allows for more complex merge conflicts, which require the user to manually modify a file in order to resolve a conflict, to be solved right form the GitLab interface. Use the Edit inline button to open the editor. Once you're sure about your changes, hit the Commit to source branch button.

Merge conflict editor

Conflicts available for resolution

GitLab allows resolving conflicts in a file where all of the below are true:

The file is text, not binary
The file is in a UTF-8 compatible encoding
The file does not already contain conflict markers
The file, with conflict markers added, is not over 200 KB in size
The file exists under the same path in both branches

If any file with conflicts in that merge request does not meet all of these criteria, the conflicts for that merge request cannot be resolved in the UI.

Additionally, GitLab does not detect conflicts in renames away from a path. For example, this will not create a conflict: on branch a, doing git mv file1 file2; on branch b, doing git mv file1 file3. Instead, both files will be present in the branch after the merge request is merged.