check_changed_files.yml

name: Check changed files

on: 
    pull_request:
        branches:
            - main

jobs:

    check-changed-files:

        runs-on: ubuntu-latest

        if: github.repository_owner == 'neurodatascience' && github.event.repository.name != 'testpoppy'

        steps:

          - name: Checkout current repository
            uses: actions/checkout@v3
            with:
                fetch-depth: 0
                path: repo_to_check

          - name: Checkout template repository
            uses: actions/checkout@v3
            with:
                repository: neurodatascience/testpoppy
                ref: main
                path: template_repo

          - name: Check changed files
            run: |
                CHANGED_FILES=$(cd repo_to_check; git diff-tree --no-commit-id --name-only -r ${{ github.event.pull_request.head.sha }} ${{ github.event.pull_request.base.sha }})
                echo -e "Checking changed files:\n${CHANGED_FILES}"
                COUNT="0"
                for FILE in ${CHANGED_FILES}; do
                    if [ -f "template_repo/${FILE}" ]; then
                        echo "::error::File exists in the template repository: ${FILE}"
                        COUNT=$((COUNT+1))
                    fi
                done
                if [ ${COUNT} -gt 0 ]
                then
                    echo "This PR modifies ${COUNT} files that also exist in the template repository."
                    exit 1
                fi