preview_comment.yaml

name: "Post preview links for changed files"

on:
    pull_request: ~

jobs:
    post-preview-links:
        name: Post preview links for changed files
        runs-on: ubuntu-latest
        permissions:
            # Needed to manage the comment
            pull-requests: write

        steps:
            - uses: actions/checkout@v4
              with:
                  fetch-depth: 0

            -   name: Create comment for changed files
                run: |
                    set -x #TMP
                    file_limit=100
                    build_url="https://ez-systems-developer-documentation--${{ github.event.pull_request.number }}.com.readthedocs.build/en/${{ github.event.pull_request.number }}/"

                    changed_files=$(git diff --name-only HEAD origin/$GITHUB_BASE_REF | grep -E ".md$" || [[ $? == 1 ]])
                    number_of__changed_files=$(echo $changed_files | wc -l)

                    if [[ $changed_files -eq "" ]] ; then
                      comment="No markdown files changed, no preview needed."
                    elif [[ $number_of__changed_files -gt file_limit ]] ; then
                      comment="Too many files modified in a single PR. Unable to post preview links, sorry!"
                    else
                      filenames=$(echo "$changed_files" | rev | cut -d / -f 1 | rev)
                      urls=$(echo "$changed_files" | cut -d / -f 2- | sed -e "s ^ $build_url ")

                      left=$(yes "- [" | head -n $number_of__changed_files )
                      middle=$(yes "](" | head -n $number_of__changed_files )
                      right=$(yes ")" | head -n $number_of__changed_files )

                      comment=$(paste -d'\0' <(echo "$left") <(echo "$filenames") <(echo "$middle") <(echo "$urls") <(echo "$right"))
                      comment="Preview of modified files:\n\n$comment"
                    fi

                    echo $comment > comment.md

            -   name: Find comment
                id: find-comment
                uses: peter-evans/find-comment@v3
                with:
                    issue-number: ${{ github.event.pull_request.number }}
                    comment-author: 'github-actions[bot]'
                    body-includes: 'Preview of modified files'

            -   name: Create or update comment
                uses: peter-evans/create-or-update-comment@v4
                with:
                    comment-id: ${{ steps.fc.outputs.comment-id }}
                    issue-number: ${{ github.event.pull_request.number }}
                    body-path: comment.md
                    edit-mode: replace