When exporting a repository using Datacenter Migrations, Pull request activities are duplicated

Issue Summary

Pull request activities which have more than one commit to an event (push for example) causes the export to duplicate the activity.

Steps to Reproduce

1. Create a pull request
2. Perform two or more commits to the source branch
3. Push the multiple commits to the pull request
4. Export and re-import the pull request

Expected Results

The pull request activites look like the original

Actual Results

The activity is duplicated based on the amount of commits under the activity

Workaround

No current work-arounds are known for this issue