Fetches the URL to download the migration archive as a tar.gz file. Depending on the resources your repository uses, the migration archive can contain JSON files with data for these objects:
attachments
bases
commit_comments
issue_comments
issue_events
issues
milestones
organizations
projects
protected_branches
pull_request_reviews
pull_requests
releases
repositories
review_comments
schema
users
The archive will also contain an attachments directory that includes all attachment files uploaded to GitHub.com and a repositories directory that contains the repository’s Git data.