Create a GitHub Release and upload multiple assets in GitHub Actions

release.yaml

name: Release

on:
  push:
    tags: ["v*"]

jobs:
  run:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2
    - run: |
        set -x
        assets=()
        for asset in ./*.md; do
          assets+=("-a" "$asset")
        done
        tag_name="${GITHUB_REF##*/}"
        hub release create "${assets[@]}" -m "$tag_name" "$tag_name"
      env:
        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}