Automated backmerge master → develop on release publishing

[AndrewSazonov]

Across EasyScience repositories, we follow a feature → develop → master branching workflow (see ADR #12 for a detailed overview).

After a release is published, the master branch may contain changes that must also be applied back to develop (for example, version bumps, hotfixes, or release-related adjustments). This ensures that any new feature branches are created from an up-to-date develop.

This “backmerge” step from master to develop is easy to forget and often requires additional manual work. If skipped, develop can fall behind master, which may lead to confusion, duplicated fixes, or inconsistencies in subsequent development.

To make this process consistent and reliable, we have an automated backmerge workflow to the EasyScience Copier templates:
https://github.com/easyscience/templates/blob/master/template/.github/workflows/backmerge.yml

This workflow automatically merges master into develop whenever a new release is published.

Trigger

The workflow is triggered:

• On release events of type published or prereleased
• Optionally via workflow_dispatch (manual trigger)

This ensures that the standard release process automatically includes a backmerge step, while still allowing manual execution if needed.

Key Behavior

• Performs a direct merge from origin/master into develop (no pull request is created)
• Adds [skip ci] to the merge commit message to avoid unnecessary CI runs
• Uses the EasyScience GitHub App token to safely bypass branch protection rules
• Exits cleanly if develop is already up-to-date with master
• Detects merge conflicts:
  • If a conflict occurs, no push is performed
  • An issue titled Backmerge conflict: master → develop is created (or reopened if it already exists)
  • A link to the failed workflow run is added for easier debugging

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Links to the related discussions: #44