Implement Maintenance Branch Releases (C5 Workflow)

[hdamker]

Problem description

After public releases, maintenance branches may require patch releases for critical fixes and security patches. The C2-C4 workflows need extension to handle maintenance scenarios with different branch sources and version constraints.

Part of #191 (Develop automation support in support of release management). See PR #338 for the full implementation plan.

Proposed solution

Extend C2-C4 workflows to support maintenance branch releases (C5, Step 6 of the release workflow):

1. Maintenance Branch Prerequisites

   • Maintenance branch exists (e.g., maintenance-r3), created from last commit included in release cycle
   • release-plan.yaml has target_release_type: maintenance-release
   • Only bug fixes allowed, no new features

2. Workflow Adaptations for Maintenance

   • Release branch created from maintenance branch (not main)
   • Version validation: patch-only increments (X.Y.Z -> X.Y.Z+n)
   • Sync PR targets maintenance branch
   • Optional backport PR to main

3. Maintenance Releases

   • Follow same C2-C4 workflow pattern
   • Consecutive numbering (r3.4, r3.5) within maintenance cycle
   • Each release may contain different patch versions per API

Dependencies

• Requires Phase 4-5 complete (base automation extends to maintenance)

Success criteria

• Maintenance releases follow automated workflow
• Tested on 2-3 repositories requiring patches
• Documentation complete

Milestone

Target completion: June 15, 2026 (Fall26 M3)

[hdamker]

Backlog item until the release automation for normal releases is productive.