# PR Commenter Diff-Aware Action

A GitHub/Gitea Action to automatically post comments to pull requests 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 values for repository info
- Optional `diff` input — can post general PR comments without a diff
- Remote URL usage for Gitea Actions

---

## 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 a single line and `{lines}` for all added lines in a file.
- **Optional diff**: If no diff is provided, posts a general PR comment.
- **Default repository values**: `repo_name`, `repo_owner`, and `api_url` default to GitHub environment variables if not provided.
- **Remote URL usage**: Can reference the action directly from a Git repository URL for Gitea.

---

## 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 | `${{ github.api_url }}` |
| `repo_owner` | Repository owner (user/org) | no | `${{ github.repository_owner }}` |
| `repo_name` | Repository name | no | `${{ github.repository }}` |
| `pr_index` | PR number (GitHub) or index (Gitea) | yes | - |
| `diff` | Git diff to parse (optional). If empty, posts only a general PR comment. | no | - |
| `comment_template` | Multiline template for comment body. Use placeholders `{line}` and `{lines}` | no | `Auto-comment: changed line -> {line}` |

---

## Example Usage

### GitHub PR

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

      - 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: "https://gitea.example.com/your-org/pr-commenter-action@main"
        with:
          platform: github
          token: ${{ secrets.GITHUB_TOKEN }}
          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}
```

### Gitea PR

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

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

      - name: Post diff-aware comments to Gitea PR
        uses: "https://gitea.example.com/your-org/pr-commenter-action@main"
        with:
          platform: gitea
          token: ${{ secrets.GITEA_TOKEN }}
          api_url: "https://gitea.example.com/api/v1"
          pr_index: 42
          diff: ${{ steps.gitdiff.outputs.diff }}
          comment_template: |
            Auto-comment on file:
            ---
            Changed line: {line}
            Full added lines in this file:
            {lines}
```