GitHub Actions workflow to open PRs for php-cs-fixer changes

fix-cs-php.yml

# Update this by running
# curl https://gist.githubusercontent.com/mpdude/ca93a185bcbf56eb7e341632ad4f8263/raw/fix-cs-php.yml > .github/workflows/fix-cs-php.yml

on:
    push:
        branches:
            - master
    pull_request:

name: Coding Standards

jobs:
    open-pr-for-cs-violations:
        name: PHP-CS-Fixer
        runs-on: ubuntu-18.04
        if: github.actor != 'dependabot[bot]'
        steps:
            -   name: Checkout code
                uses: actions/checkout@v2
                with:
                    ref: ${{ github.head_ref }}

            -   name: Run PHP-CS-Fixer
                uses: docker://oskarstark/php-cs-fixer-ga:2.16.7

            -   name: Create PR for CS fixups
                uses: peter-evans/create-pull-request@9825ae65b1cb54b543b938503728b432a0176d29
                id: create-pull-request
                with:
                    token: ${{ secrets.GITHUB_TOKEN }}
                    title: Fix coding standards in ${{ github.ref }}
                    branch: php-cs-fixer/${{ github.ref }}
                    assignees: ${{ github.actor }}
                    labels: php-cs-fixer
                    body: Please merge these changes into the ${{ github.ref }} branch to fix coding standard violations.
                    commit-message: Apply php-cs-fixer changes as of ${{ github.sha }}

            -   name: Leave a notice in the discussion when fixing code in a Pull Request
                uses: docker://mpdude/comment-on-pr:v1.2.0
                env:
                    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
                if: steps.create-pull-request.outputs.pr_number # only if PR was created in the previous step
                continue-on-error: true # continue on failure - necessary when the current branch does not have a pending PR
                with:
                    msg: |
                        @${{ github.actor }} please apply the coding standard fixes from #${{ steps.create-pull-request.outputs.pr_number }}

            -   name: Fail the workflow when necessary CS fixes were detected
                run: echo "Failing workflow run because CS violations were detected." && exit 1
                if: steps.create-pull-request.outputs.pr_number

Drop the above file into .github/workflows; and of course, make sure you have .php_cs.dist checked in and .php_cs.cache in your .gitignore.

This action will then run php-cs-fixer for all pushed commits. If changes need to be made, a PR will be opened so you can review and merge them. If the offending commit was already part of a PR, a comment will also be left in the discussion of that PR.