Document required permissions for migration archive in ghe-migrator prepare step

[megamanics]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://github.com/github/docs/blob/main/content/migrations/using-ghe-migrator/migrating-data-to-github-enterprise-server.md

What part(s) of the article would you like to see updated?

Please update the documentation to specify that the migration archive (e.g. MIGRATION-GUID.tar.gz) must have sufficient read permissions for the user running ghe-migrator prepare. An error occurs if the default permissions do not allow reading the archive. Suggest adding a troubleshooting note and a permissions check, e.g. chmod 644 migration_archive.tar.gz, before running the prepare step.

Additional information

Error occurs at the ghe-migrator prepare step due to insufficient file permissions. Reproducible by attempting to prepare an archive owned by a different user or with restrictive permissions. A bash one-liner to fix:

chmod 644 migration_archive.tar.gz

Error from ghe-migrator:

The prepare failed to complete. Log statements have been emitted to container logs.

Please contact GitHub Enterprise Support via https://support.github.com.

Log statements emitted to container STDOUT and can be found in container logs with log field InstrumentationScope='GitHubMigratorCli'