Mirror Sync

Automated sync for mirroring GitHub repositories to greptileai/*-mirror repos.

What it does

Every 30 minutes, this workflow syncs configured repositories in parallel:

1. Syncs all branches - Force-pushes all branches from upstream
2. Syncs tags - Pushes all tags from upstream
3. Syncs labels - Copies labels from upstream repo
4. Syncs PRs - For every open PR on upstream:
   • Creates a corresponding branch on the mirror
   • Creates a corresponding PR with the same title and description
   • Updates branches when upstream PRs are updated
   • Closes mirror PRs when upstream PRs are closed/merged

Adding a new repo

1. Edit repos.yaml and add a new entry:

repos:
  - name: react
    upstream: facebook/react
    mirror: greptileai/react-mirror
    excluded_prs: [32222]

  - name: nextjs          # Add your repo
    upstream: vercel/next.js
    mirror: greptileai/nextjs-mirror
    excluded_prs: []

2. Create the mirror repository on GitHub (e.g., greptileai/nextjs-mirror)

3. Ensure your MIRROR_PAT has access to the new mirror repo

4. Commit and push - the workflow will start syncing on the next run

Configuration

repos.yaml fields

Field	Description
name	Short identifier for logging
upstream	Source repository (e.g., facebook/react)
mirror	Destination repository (e.g., greptileai/react-mirror)
excluded_prs	List of PR numbers to skip (e.g., branch name collisions)

Setup

1. Create a Personal Access Token (PAT)

Create a PAT with the following permissions:

• repo (full control of private repositories)
• workflow (update GitHub Action workflows)

The PAT must have access to all mirror repositories under greptileai/.

2. Add the secret

Add the PAT as a repository secret named MIRROR_PAT:

1. Go to this repo's Settings > Secrets and variables > Actions
2. Click "New repository secret"
3. Name: MIRROR_PAT
4. Value: Your PAT

3. Enable the workflow

The workflow runs automatically every 30 minutes. You can also trigger it manually from the Actions tab.

Manual trigger

Go to Actions > "Sync Mirror Repos" > "Run workflow"

Architecture

repos.yaml                    # Central config defining all repo pairs
  |
sync.yml (matrix strategy)    # GitHub Actions runs jobs in parallel
  |
sync_mirror.py (parameterized)  # Python script accepts repo config as args

• Jobs run in parallel (up to 5 concurrent) with fail-fast: false
• One repo failure doesn't affect others
• Each sync job is independent (no shared state)