From git diff to perfect PR description in 2 minutes using Claude

# Add to ~/.zshrc or ~/.bashrc

pr-describe() {
  local base_branch="${1:-main}"
  local diff_output

  diff_output=$(git diff "${base_branch}...HEAD" 2>&1)

  if [ -z "$diff_output" ]; then
    echo "No diff found against ${base_branch}. Are you on a feature branch?"
    return 1
  fi

  echo "Generating PR description..."

  echo "$diff_output" | claude --print     --system "You are a senior engineer writing a GitHub pull request description.
Output a structured PR description with these sections:
## Summary
One paragraph explaining what this PR does and why.

## Changes
Bullet list of specific changes made.

## Testing
How the changes were tested or how a reviewer can verify them.

## Notes
Any migration steps, breaking changes, or important reviewer callouts.

Be specific and technical. Infer intent from the code changes.
Format for GitHub markdown."     "Write a PR description for this diff:" 
}

# Also useful: copy to clipboard
pr-describe-copy() {
  pr-describe "$@" | pbcopy
  echo "PR description copied to clipboard"
}

npm install -g @anthropic-ai/claude-code

# Set your API key
export ANTHROPIC_API_KEY="your-key-here"

#!/usr/bin/env python3
# pr-describe.py — place in ~/bin/ and chmod +x

import sys
import subprocess
import anthropic

def get_diff(base_branch: str = "main") -> str:
    result = subprocess.run(
        ["git", "diff", f"{base_branch}...HEAD"],
        capture_output=True, text=True
    )
    return result.stdout

def generate_pr_description(diff: str) -> str:
    client = anthropic.Anthropic()
    
    # Truncate very large diffs to fit context window
    max_diff_chars = 50_000
    if len(diff) > max_diff_chars:
        diff = diff[:max_diff_chars] + "

[Diff truncated — showing first 50k chars]"
    
    response = client.messages.create(
        model="claude-opus-4-5",
        max_tokens=1500,
        system="""You are a senior engineer writing a GitHub pull request description.
Write a clear, structured PR description with:
- ## Summary: What this PR does and why (1-2 paragraphs)
- ## Changes: Specific changes as bullet points
- ## Testing: How changes were tested
- ## Notes: Breaking changes, migrations, or reviewer callouts (if any)
Be specific and technical. Infer intent from the code.""",
        messages=[
            {
                "role": "user",
                "content": f"Write a PR description for this git diff:

{diff}"
            }
        ],
    )
    return response.content[0].text

if __name__ == "__main__":
    base = sys.argv[1] if len(sys.argv) > 1 else "main"
    diff = get_diff(base)
    
    if not diff.strip():
        print(f"No diff against {base}")
        sys.exit(1)
    
    print(generate_pr_description(diff))

# In ~/.zshrc
pr-describe() {
  python3 ~/bin/pr-describe.py "${1:-main}"
}

pr-describe-copy() {
  pr-describe "$@" | pbcopy && echo "Copied to clipboard"
}

## Summary
Migrates JWT validation from HS256 (shared secret) to RS256 (public/private key pair).
This improves security posture by allowing downstream services to validate tokens
without access to the signing secret. Public key is distributed via environment variable.

## Changes
- Replace `jwt.sign(payload, SECRET)` with `jwt.sign(payload, PRIVATE_KEY, { algorithm: 'RS256' })`
- Add `RS256_PRIVATE_KEY` and `RS256_PUBLIC_KEY` to environment config
- Update all downstream service token validation to use public key
- Add `scripts/generate-keys.sh` for local key generation
- Update integration tests to use RSA key fixtures

## Testing
- All 47 existing auth tests pass with new implementation
- New tests added for: key rotation, malformed key errors, algorithm mismatch
- Tested locally with `scripts/generate-keys.sh` workflow

## Notes
⚠️ Breaking change: requires `RS256_PRIVATE_KEY` and `RS256_PUBLIC_KEY` env vars.
Update deployment configs before merging.
Old `JWT_SECRET` env var is no longer read.