PR Commenter Diff-Aware Action

A GitHub Action to automatically post comments to pull requests on GitHub or Gitea, based on a git diff. Supports:

• Inline comments per changed line
• Multiline comment templates
• Cross-platform support (GitHub and Gitea)
• Diff-aware commenting, automatically detecting added lines
• Default comment template with optional overrides

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Features

• GitHub & Gitea support: Works seamlessly on both platforms.
• Diff-aware: Parses a git diff to determine which lines were added.
• Inline comments: Comments appear directly on changed lines in PRs.
• Multiline templates: Supports {line} for single line and {lines} for all added lines in a file.
• Reusable: Works as a composite action and can be called from any workflow.

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Inputs

Input	Description	Required	Default
platform	Target platform: github or gitea	yes	github
token	API token for authentication	yes	-
api_url	Gitea API URL (only required for Gitea, e.g., https://gitea.example.com/api/v1)	no	-
repo_owner	Repository owner (user/org)	yes	-
repo_name	Repository name	yes	-
pr_index	PR number (GitHub) or index (Gitea)	yes	-
diff	Git diff to parse (generated via git diff)	yes	-
comment_template	Multiline template for comment body. Use {line} for a single line and {lines} for all added lines in the file	yes	Auto-comment: changed line -> {line}

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Example Usage

jobs:
  comment-pr-diff:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: "3.11"

      - name: Generate git diff
        id: gitdiff
        run: |
          git fetch origin main
          git diff origin/main > diff.txt

      - name: Post diff-aware comments to GitHub PR
        uses: ./  # path to this action
        with:
          platform: github
          token: ${{ secrets.GITHUB_TOKEN }}
          repo_owner: ${{ github.repository_owner }}
          repo_name: ${{ github.event.repository.name }}
          pr_index: ${{ github.event.pull_request.number }}
          diff: ${{ steps.gitdiff.outputs.diff }}
          comment_template: |
            Auto-comment on file:
            ---
            Changed line: {line}
            Full added lines in this file:
            {lines}