Project Import: failing to import merge requests with "undefined method repository' for nil:NilClass\n\n target_project.repository.fetch_source_branch!(source_project.repository, source_branch, ref_path)`

File-based Project Import and Direct Transfer sometimes fails to import merge requests with the following error:

"undefined method repository' for nil:NilClass\n\n target_project.repository.fetch_source_branch!(source_project.repository, source_branch, ref_path)\n `,

Investigate why this is happening and ensure the MRs are being migrated.

Update

This was closed and

Backend: Record skipped MR import and make available via... (#537939)

Frontend: Show skipped MRs in project import statistics (#537943)

were created. They should address the only (known) reproduction case for this issue.