action.yml

name: Update config branch
description: Updates the config-only branch and creates a PR if there are any changes.
# This works as part of automating config export. A cron job on Platform.sh
# periodically updates an intermediate config repo with the latest config. The
# config repo only contains config, it doesn't share a history with the site
# repo. This workflow keeps a branch on the site repo up-to-date with a branch
# on the config repo. Whenever the local config-only branch gets updated, the
# workflow creates a PR. If a PR already exists, the branch will just be
# updated. One or more users can be notified.
#
# Workflow permissions:
# The repo calling this must be configured to support GitHub actions making PRs.

inputs:
  config_repo:
    description: The GitHub config repo, eg. MyOrg/MySiteConfig.
    type: string
    required: true
  config_repo_token:
    description: A token with read access to the config repository.
    type: string
    required: true
  config_repo_branch:
    description: The branch on the config repository.
    type: string
    required: true
    default: main
  site_repo:
    description: The GitHub Drupal site repo, eg. MyOrg/MySite
    type: string
    required: true
    default: ${{ github.repository }}
  site_repo_token:
    description: The GitHub Drupal site repo token with access to write contents and create PRs.
    type: string
    required: true
    default: ${{ github.token }}
  site_repo_config_branch:
    description: The branch on the site repository that mirrors the config repository.
    type: string
    required: true
    default: config-only
  site_repo_live_branch:
    description: The name of the live branch (ie the one that's currently deployed).
    type: string
    default: main
    required: true
  site_repo_pr_branch:
    description: The name of the topic branch to create on the site repository with config changes.
    type: string
    required: true
    default: automatic-config-export
  site_repo_pr_branch_base:
    description: The branch on the site repository from which to create the PR branch.
    type: string
    required: true
    default: staging
  committer_name:
    description: The name used on the git merge commit.
    type: string
    required: true
    default: R2D2
  committer_email:
    description: The email used on the git merge commit.
    type: string
    required: true
    default: update-config@example.com
  github_notify:
    description: A space-separated list of github users including '@' to ping on a new PR, eg. '@andy @becca'.
    type: string

runs:
  using: composite
  steps:
    # Optimize for the normal case that the two branches are the same. So start
    # by doing a shallow checkout of both and checking their hashes. If they're
    # different, then do a full checkout to enable a merge.
    - uses: actions/checkout@v4
      id: checkout_site_repo_config_branch
      with:
        repository: ${{ inputs.site_repo }}
        ref: ${{ inputs.site_repo_config_branch }}
        token: ${{ inputs.site_repo_token }}
        path: local
      # It might error if the config-only branch doesn't exist yet.
      continue-on-error: true

    - uses: actions/checkout@v4
      if: ${{ steps.checkout_site_repo_config_branch.outcome == 'failure' }}
      with:
        repository: ${{ inputs.site_repo }}
        token: ${{ inputs.site_repo_token }}
        path: local

    - uses: actions/checkout@v4
      with:
        repository: ${{ inputs.config_repo }}
        ref: ${{ inputs.config_repo_branch }}
        token: ${{ inputs.config_repo_token }}
        # If we failed to checkout the site repo config branch, we'll need a
        # full checkout to set it up.
        fetch-depth: ${{ steps.checkout_site_repo_config_branch.outcome != 'failure' && '1' || '0' }}
        path: remote

    - name: Create the site repository config-only branch if necessary.
      if: ${{ steps.checkout_site_repo_config_branch.outcome == 'failure' }}
      shell: sh
      run: |
        # Create the site repository config-only branch if necessary.
        set -eu
        cd local
        git remote add remote-config ../remote
        git fetch remote-config
        git checkout -b ${{ inputs.site_repo_config_branch }} remote-config/${{ inputs.config_repo_branch }}
        git push origin HEAD
        git remote remove remote-config
        echo 'Created the branch `${{ inputs.site_repo_config_branch }}` to mirror `${{ inputs.config_repo }}:${{ inputs.config_repo_branch }}`.' >> $GITHUB_STEP_SUMMARY

    - name: Read HEAD from new branches
      shell: sh
      run: |
        # Read HEAD from new branches
        set -eu
        local_head=$(git -C local rev-parse HEAD)
        remote_head=$(git -C remote rev-parse HEAD)
        echo "local_head=$local_head" >> "$GITHUB_ENV"
        echo "remote_head=$remote_head" >> "$GITHUB_ENV"
        if [ "$local_head" = "$remote_head" ]; then
          echo 'The local config branch `${{ inputs.site_repo_config_branch }}` is up-to-date with the remote. No further action required.' >> $GITHUB_STEP_SUMMARY
        fi

    - uses: actions/checkout@v4
      if: ${{ env.local_head != env.remote_head }}
      with:
        repository: ${{ inputs.site_repo }}
        ref: ${{ inputs.site_repo_config_branch }}
        token: ${{ inputs.site_repo_token }}
        fetch-depth: 0
        path: local

    - uses: actions/checkout@v4
      # If the repo config branch was created then we already have a full
      # checkout.
      if: ${{ env.local_head != env.remote_head && steps.checkout_site_repo_config_branch.outcome != 'failure' }}
      with:
        repository: ${{ inputs.config_repo }}
        ref: ${{ inputs.config_repo_branch }}
        path: remote
        token: ${{ inputs.config_repo_token }}
        fetch-depth: 0

    - name: Update the local config-only branch from the remote
      if: ${{ env.local_head != env.remote_head }}
      working-directory: local
      shell: sh
      run: |
        # Update the local config-only branch from the remote
        set -eu
        git remote add remote-config ../remote
        git fetch remote-config
        git reset --hard remote-config/${{ inputs.config_repo_branch }}
        git push origin HEAD

    - name: Create a site branch with the config and open a PR
      if: ${{ env.local_head != env.remote_head }}
      working-directory: local
      env:
        GH_TOKEN: ${{ inputs.site_repo_token }}
      shell: bash
      run: |
        # Create a site branch with the config and open a PR
        set -eu
        source_branch=${{ inputs.site_repo_pr_branch }}
        if ! git show-branch remotes/origin/${{ inputs.site_repo_pr_branch }} &> /dev/null; then
          git branch ${{ inputs.site_repo_pr_branch }} origin/${{ inputs.site_repo_live_branch }}
          source_branch=${{ inputs.site_repo_pr_branch_base }}
        fi
        git checkout ${{ inputs.site_repo_pr_branch }}
        
        cd config/sync
        rm *
        mv "$GITHUB_WORKSPACE"/remote/* .
        git add .
        if [[ -n "$(git status --porcelain)" ]]; then
          git config user.name '${{ inputs.committer_name }}'
          git config user.email '${{ inputs.committer_email }}'
          git commit -m "Export config from Prod" -m "${{ inputs.config_repo }}:$remote_head"
          git push origin HEAD
          echo 'Updated the config in branch `${{ inputs.site_repo_config_branch }}`.' >> $GITHUB_STEP_SUMMARY
          # Create a PR if there isn't already one.
          if [[ "$(gh pr list --head ${{ inputs.site_repo_pr_branch }} --json id)" == "[]" ]]; then 
            pr_url=$(gh pr create \
              -B ${{ inputs.site_repo_pr_branch_base }} \
              -H ${{ inputs.site_repo_pr_branch }} \
              --title 'Merge latest config export into ${{ inputs.site_repo_pr_branch_base }}' \
              --body 'PR created automatically by update-config. ${{ inputs.github_notify }}')
            echo "[Created a PR]($pr_url) to merge the changes back into \`${{ inputs.site_repo_pr_branch_base }}\`. " >> $GITHUB_STEP_SUMMARY
          else
            echo "A PR for the branch already exists. No further action required." >> $GITHUB_STEP_SUMMARY
          fi
        else
          echo "Branch \`${{ inputs.site_repo_config_branch }}\` has been updated, but the changes match what's already in branch \`$source_branch\`. No further action required." >> $GITHUB_STEP_SUMMARY
        fi