Comment-on-diff

This github action adds a comment on a pull request depending on which files are modified.

Usage

To use it you need a github workflow like this:

name: Notices
on: [pull_request]
jobs:
  build:
    name: Send notices
    runs-on: ubuntu-latest
    steps:
      - name: Check out code
        uses: actions/checkout@v4
      - name: Fetch branches
        run: |
          git fetch --no-tags --prune --depth=100 origin "+refs/heads/${BASE}:refs/remotes/origin/${BASE}"
          git fetch --no-tags --prune --depth=100 origin "+refs/heads/${HEAD}:refs/remotes/origin/${HEAD}"
        env:
          BASE: ${{ github.base_ref }}
          HEAD: ${{ github.head_ref }}
      - name: Comment on diff
        uses: MeilleursAgents/comment-on-diff@master
        with:
          base: ${{ github.event.pull_request.base.sha }}
          head: ${{ github.event.pull_request.head.sha }}
          github_token: ${{ secrets.GITHUB_TOKEN }}

Configuration

You need a config file named .github/comment-on-diff.yaml, wich is a YAML dict where keys are paths regexes and value are the message to send.

Example:

main.py: You have changed the main.py file, don't forget to run the linter.
some/folder: Any modification on this folder implies you agree with something.
.+/a?b.py: hey looks at that regex!

With this a modification on those files will trigger a comment with the corresponding message:

• main.py: "You have changed…"
• some/folder/any/file: "Any modification…"
• something/ab.py: "hey…"
• somethingelse/very/far/away/b.py: "hey…"

Beware that the regex is matched from the start of the file path, so ab?c.py would match abc.py but not somewhere/abc.py.

The messages can be on multiple lines and can use markdown.

The action takes care of not sending twice the same message, to not spam the PR.

Anti match

You can also trigger a comment when a file is not modified. For that you need to use the extended config structure, like this:

CHANGELOG.md:
  msg: You need to edit the changelog
  absent: true

This configuration will trigger a comment when no diff is found for "CHANGELOG.md".