preview-pointer.yaml

name: 'preview-pointer'

# Preview builds check a single fixed URL for updates:
#   releases/download/preview/latest.json
#
# GitHub has no "latest including pre-releases" redirect, so that URL is a
# permanent pointer release whose only asset is the manifest, re-pointed here
# on every publish.
#
# It tracks the newest build of EITHER channel on purpose. Refreshing it when a
# stable release publishes is what carries preview users onto the official
# build instead of stranding them on the last preview; once they install it,
# their client is a stable build reading the stable endpoint, and the two
# channels have converged.
on:
  release:
    types: [published]

jobs:
  repoint:
    # Uploading to the pointer publishes nothing, but guard anyway so a manual
    # edit of the pointer release can never re-trigger this.
    if: github.event.release.tag_name != 'preview'
    runs-on: ubuntu-latest
    permissions:
      contents: write

    steps:
      - name: Point the preview channel at ${{ github.event.release.tag_name }}
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          TAG: ${{ github.event.release.tag_name }}
        run: |
          set -euo pipefail

          if ! gh release download "$TAG" --repo "$GITHUB_REPOSITORY" \
                 --pattern latest.json --dir . --clobber 2>/dev/null; then
            echo "::warning::$TAG has no latest.json asset; preview channel left unchanged."
            exit 0
          fi

          echo "Manifest version: $(jq -r .version latest.json)"

          # `--prerelease` is load-bearing: without it the pointer would become
          # the repo's /releases/latest and serve previews to the stable channel.
          if ! gh release view preview --repo "$GITHUB_REPOSITORY" >/dev/null 2>&1; then
            gh release create preview \
              --repo "$GITHUB_REPOSITORY" \
              --prerelease \
              --title 'Preview channel' \
              --notes 'Update manifest for Vector preview builds. Nothing to download here; the manifest points at the real release.'
          fi

          gh release upload preview latest.json --clobber --repo "$GITHUB_REPOSITORY"