ci: trigger repeater docker rebuilds when core changes

[yellowcooln]

PR Summary

This PR adds a GitHub Actions workflow to pyMC_core that automatically triggers a pyMC_Repeater Docker image rebuild whenever pyMC_core main or dev changes.

The goal is to keep published repeater images aligned with the current core branch automatically, without requiring manual rebuilds every time pyMC_core advances.

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What It Does

The new workflow runs on:

• Pushes to main
• Pushes to dev
• Optional manual workflow_dispatch

When triggered, it:

• Determines the current channel from the branch name (main or dev)

• Selects the repeater repository to notify:

  • pyMC-dev/pyMC_Repeater

• Sends a repository_dispatch event to the repeater repo

• Includes:

  • channel
  • core_ref
  • Exact core_sha

This allows the repeater repo’s Docker publish workflow to rebuild the matching image channel using the exact current core commit.

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Why This Is Needed

pyMC_Repeater Docker images bundle pyMC_core, but repeater images are only rebuilt when repeater CI itself runs.

Without this workflow:

• pyMC_core can move forward
• Repeater Docker images can remain stale
• Users can pull a fresh repeater image tag that still contains an older core commit

This workflow closes that gap by proactively triggering repeater rebuilds whenever core changes.

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File Added

• .github/workflows/trigger-repeater-docker-rebuild.yml

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Behavior

• dev core changes trigger repeater dev rebuilds
• main core changes trigger repeater main rebuilds
• No manual core commit entry is required
• Exact core commit SHAs are passed through automatically

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Required Secret

This workflow requires a repository secret in the pyMC_core repo:

• REPEATER_REPO_DISPATCH_TOKEN

The token is used to call:

POST /repos/<repeater-repo>/dispatches

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Token Permissions

Recommended

Use a fine-grained GitHub Personal Access Token.

Minimum Access

Repository access to the target repeater repo with:

• Actions:

  • Read and write

• Contents:

  • Read-only

Classic PAT Alternative

If using a classic PAT instead:

• repo scope is typically sufficient
• Fine-grained tokens are still preferred

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Creating the Token

On the GitHub account that owns or has access to the target repeater repo:

1. Open GitHub Settings

2. Go to:

   • Developer settings

3. Open:

   • Personal access tokens

4. Create:

   • Fine-grained token

5. Select the target repeater repo:

   • pyMC-dev/pyMC_Repeater

6. Grant the required permissions

7. Copy the token

8. Add it to the pyMC_core repo as:

   • REPEATER_REPO_DISPATCH_TOKEN

Path:

• Settings
• Secrets and variables
• Actions
• New repository secret

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Important Note

This workflow only sends the dispatch event.

The repeater repo must already contain the matching repository_dispatch handler workflow on its default branch, otherwise no rebuild will occur.

The full chain requires:

1. Repeater workflow support for repository_dispatch
2. This core dispatch workflow
3. REPEATER_REPO_DISPATCH_TOKEN configured in pyMC_core

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Result

Once both sides are merged and the secret is configured:

• Merging to pyMC_core/dev automatically rebuilds repeater dev
• Merging to pyMC_core/main automatically rebuilds repeater main
• Published repeater Docker images stay aligned with the current core branch automatically