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

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

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}