Sync any number of GitHub repo mirrors regularly

A simple GitHub workflow to regularly sync multiple repository mirrors (i.e. identical forks).

All mirrors are synced in parallel. Each mirror is forked from its upstream repository, if necessary. The GitHub workflow is scheduled to automatically run once a week (on Sunday), but can also be triggered manually.

Note that the workflow uses a simple git push (i.e. it does NOT force push) to the mirror. This means that if commits were force-pushed to the upstream repository branch which would overwrite existing commits in the mirror, the sync job for this repo will fail and the mirror will need to be synced manually. This is on purpose, and we recommend not force-pushing to the main branch of your repository.

If you'd like to have your repository mirrored on the Earlham Institute GitHub organisation, please:

1. Fork this repository.
2. Modify the .github/workflows/sync.yaml file by adding a new job configuration to the matrix of the repo-sync job as in these lines.
3. Open a pull request.