Automated git-submodule updates via PR

ci-update-submodules.yml

name: Update git submodules

on:
  pull_request:
    branches: ["main"]
    paths:
      - ".github/workflows/ci-update-submodules.yml"
  schedule:
    # on Sundays
    - cron: "0 0 * * 0"
  workflow_dispatch: {}

jobs:
  submodule-update:
    runs-on: "ubuntu-22.04"
    permissions:
      contents: write
      pull-requests: write
    strategy:
      fail-fast: false
      matrix:
        submodule: ["ABC"]
    defaults:
      run:
        shell: bash
    steps:
      - name: Checkout repo
        uses: actions/checkout@v4
        with:
          submodules: true
          fetch-depth: 0

      - name: initial state
        run: |
          git submodule status
          # starting from second char as the line starts with +
          short_sha=$(git submodule status | grep -A 1 ${{ matrix.submodule }} | cut -c2-9)
          echo "SHA_ACTUAL=$short_sha" >> $GITHUB_ENV
      - name: update submodules
        env:
          # verbose for eventual debugging
          GIT_TRACE: 1
        run: |
          git submodule sync
          git submodule update --remote --force
      - name: final state
        run: |
          git status
          git submodule status
          # starting from second char as the line starts with +
          short_sha=$(git submodule status | grep -A 1 ${{ matrix.submodule }} | cut -c2-9)
          echo "SHA_LATEST=$short_sha" >> $GITHUB_ENV

      - name: Create Pull Request
        # create PR with cron or dispatch if there is any change
        if: ${{ github.event_name != 'pull_request' && env.SHA_ACTUAL != env.SHA_LATEST }}
        uses: peter-evans/create-pull-request@v5
        with:
          title: "deps: update ref to latest ${{ matrix.submodule }}"
          committer: GitHub <noreply@github.com>
          author: ${{ github.actor }} <${{ github.actor }}@users.noreply.github.com>
          # when you want to update only one submodule
          add-paths: ${{ matrix.submodule }}
          commit-message: "update submodule to `${{ env.SHA_LATEST }}`"
          branch: "bump/update-${{ matrix.submodule }}"
          # Delete the branch when closing pull requests, and when undeleted after merging.
          delete-branch: true
          # the PR's body/content
          body: "**This is automated update with the latest ${{ matrix.submodule }}!**"
          labels: enhancement