pr-gfm-validator

# PR GFM Link Validator

Validate and auto-convert GFM links in pull request descriptions to prevent 404 errors.

## When to Use This Skill

This skill triggers when:

- Creating a pull request from a feature branch
- Discussing PR descriptions or body content
- Mentioning GFM links, PR links, or link validation
- Using `gh pr create` or `gh pr edit`

## The Problem

Repository-relative links in PR descriptions resolve to the **base branch** (main), not the feature branch:

| Link in PR Body            | GitHub Resolves To            | Result                            |
| -------------------------- | ----------------------------- | --------------------------------- |
| `[ADR](/docs/adr/file.md)` | `/blob/main/docs/adr/file.md` | 404 (file only on feature branch) |

## The Solution

Convert repo-relative links to absolute blob URLs with the correct branch:

```
/docs/adr/file.md
    ↓
https://github.com/{owner}/{repo}/blob/{branch}/docs/adr/file.md
```

---

## Workflow

### Step 1: Detect Context

Before any PR operation, gather repository context:

```bash
/usr/bin/env bash << 'PREFLIGHT_EOF'
# Get repo owner and name
gh repo view --json nameWithOwner --jq '.nameWithOwner'

# Get current branch
git rev-parse --abbrev-ref HEAD

# Check if on feature branch (not main/master)
BRANCH=$(git rev-parse --abbrev-ref HEAD)
if [[ "$BRANCH" == "main" || "$BRANCH" == "master" ]]; then
  echo "On default branch - no conversion needed"
  exit 0
fi
PREFLIGHT_EOF
```

### Step 2: Identify Links to Convert

Scan PR body for GFM links matching these patterns:

**CONVERT these patterns:**

- `/path/to/file.md` - Repo-root relative
- `./relative/path.md` - Current-directory relative
- `../parent/path.md` - Parent-directory relative

**SKIP these patterns:**

- `https://...` - Already absolute URLs
- `http://...` - Already absolute URLs
- `#anchor` - In-page anchors
- `mailto:...` - Email links

### Step 3: Construct Blob URLs

For each link to convert:

```python
# Pattern
f"https://