github actions submodule workflow

My personal website utilizes my zets/ repository from GitHub to generate content.

In order to create a clean continuous deployment process I leveraged GitHub Actions to update a submodule of the zets/ repo. This helped to keep my notes repo entirely separate from the actual site, something that I wanted to be sure I could maintain.

Adding the submodule

The submodule is added and updated using the below commands. This requires a .gitmodules file as well.

# add the repo
git submodule add https://github.com/username/repo

# initialize from the `.gitmodules`
git submodule update --init --recursive
git submodule udpate --recursive --remote

Drafting the GitHub Action

The action itself is set to run nightly at midnight. The scheduling was chosen for two reasons:

1. I often don't know when I'll be writing in my notes folder.
2. If it was scheduled on push to the zets/ child repo the action would be in 2 parts:
   1. Child -> parent updating
   2. Parent committing

By having a schedule I was able to mitigate this and keep things separate, which was my goal from the start.

Sources for the build:

1. A portion of this StackOverflow comment
2. The same StackOverflow thread, different portion
3. This site for Cron job scheduling

This is my actual submodules.yml file for the workflow. I used a "private access token" on GitHub specific to this repo only, use these at your discretion.

GitHub links to set this up:

1. Personal Access Tokens
2. Secrets: https://github.com/username/repo/settings/secrets/actions

name: Update Submodules
on:
  schedule:
  # run daily at midnight
  - cron: '0 0 * * *'
  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:

jobs:
  update:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2

        # Uses the private access token from above link
        with:
          token: ${{ secrets.PRIVATE_TOKEN_GITHUB }}

      # Initialize or update each one recursively
      - name: Pull & update submodules recursively
        run: |
          git submodule update --init --recursive
          git submodule update --recursive --remote

      # Commit to the repo under the GitHub actions user to ensure we have
      # reasonable logging to trace back
      - name: Commit & push changes
        run: |
          git config --global user.email "[email protected]"
          git config --global user.name "GitHub Actions - update submodules"
          git commit -am "Update submodules" || echo "No changes to commit"
          git push