updateSubmodules.yml

# https://stackoverflow.com/questions/64407333/using-github-actions-to-automatically-update-the-repos-submodules
name: 'Submodules Sync'

on:
  # Allows you to run this workflow manually from the Actions tab or through HTTP API
  workflow_dispatch:

jobs:
  sync:
    name: 'Submodules Sync'
    runs-on: ubuntu-latest

    # Use the Bash shell regardless whether the GitHub Actions runner is ubuntu-latest, macos-latest, or windows-latest
    defaults:
      run:
        shell: bash

    steps:
    # Checkout the repository to the GitHub Actions runner
    - name: Checkout
      uses: actions/checkout@v2
      with:
        submodules: false
        
    # Update references
    - name: Git Sumbodule Update
      run: |
        git submodule update --init --recursive
        git submodule update --recursive --remote

    - name: Commit update
      run: |
        git config --global user.name 'GitHub bot'
        git config --global user.email 'bot@noreply.github.com'
        git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/${{ github.repository }}
        git commit -am "Auto updated submodule" && git push || echo "No changes to commit"