name: Main PR target guard

# `main` is a pointer moved by Promote Dev to Main. Contributor and bot
# feature work lands on dev. A PR opened against main (like the GHCR
# fork PR) is what puts unique commits on main and fans the network graph.
on:
  pull_request:
    branches: [main]

permissions:
  contents: read

jobs:
  reject:
    runs-on: ubuntu-latest
    steps:
      - name: Reject pull requests targeting main
        run: |
          echo '::error::Open this PR against dev, not main. main is updated only by Promote Dev to Main.'
          exit 1