github-code-review

What this skill does

# GitHub Code Review

Perform code reviews on local changes before pushing, or review open PRs on GitHub. Most of this skill uses plain `git` — the `gh`/`curl` split only matters for PR-level interactions.

## Prerequisites

- Authenticated with GitHub (see `github-auth` skill)
- Inside a git repository

### Setup (for PR interactions)

```bash
if command -v gh &>/dev/null && gh auth status &>/dev/null; then
  AUTH="gh"
else
  AUTH="git"
  if [ -z "$GITHUB_TOKEN" ]; then
    if [ -f ~/.hermes/.env ] && grep -q "^GITHUB_TOKEN=" ~/.hermes/.env; then
      GITHUB_TOKEN=$(grep "^GITHUB_TOKEN=" ~/.hermes/.env | head -1 | cut -d= -f2 | tr -d '\n\r')
    elif grep -q "github.com" ~/.git-credentials 2>/dev/null; then
      GITHUB_TOKEN=$(grep "github.com" ~/.git-credentials 2>/dev/null | head -1 | sed 's|https://[^:]*:\([^@]*\)@.*|\1|')
    fi
  fi
fi

REMOTE_URL=$(git remote get-url origin)
OWNER_REPO=$(echo "$REMOTE_URL" | sed -E 's|.*github\.com[:/]||; s|\.git$||')
OWNER=$(echo "$OWNER_REPO" | cut -d/ -f1)
REPO=$(echo "$OWNER_REPO" | cut -d/ -f2)
```

---

## 1. Reviewing Local Changes (Pre-Push)

This is pure `git` — works everywhere, no API needed.

### Get the Diff

```bash
# Staged changes (what would be committed)
git diff --staged

# All changes vs main (what a PR would contain)
git diff main...HEAD

# File names only
git diff main...HEAD --name-only

# Stat summary (insertions/deletions per file)
git diff main...HEAD --stat
```

### Review Strategy

1. **Get the big picture first:**

```bash
git diff main...HEAD --stat
git log main..HEAD --oneline
```

2. **Review file by file** — use `read_file` on changed files for full context, and the diff to see what changed:

```bash
git diff main...HEAD -- src/auth/login.py
```

3. **Check for common issues:**

```bash
# Debug statements, TODOs, console.logs left behind
git diff main...HEAD | grep -n "print(\|console\.log\|TODO\|FIXME\|HACK\|XXX\|debugger"

# Large files accidentally staged
git diff main...HEAD --stat | sort -t'|' -k2 -rn | head -10

# Secrets or credential patterns
git diff main...HEAD | grep -in "password\|secret\|api_key\|token.*=\|private_key"

# Merge conflict markers
git diff main...HEAD | grep -n "<<<<<<\|>>>>>>\|======="
```

4. **Present structured feedback** to the user.

### Review Output Format

When reviewing local changes, present findings in this structure:

```
## Code Review Summary

### Critical
- **src/auth.py:45** — SQL injection: user input passed directly to query.
  Suggestion: Use parameterized queries.

### Warnings
- **src/models/user.py:23** — Password stored in plaintext. Use bcrypt or argon2.
- **src/api/routes.py:112** — No rate limiting on login endpoint.

### Suggestions
- **src/utils/helpers.py:8** — Duplicates logic in `src/core/utils.py:34`. Consolidate.
- **tests/test_auth.py** — Missing edge case: expired token test.

### Looks Good
- Clean separation of concerns in the middleware layer
- Good test coverage for the happy path
```

---

## 2. Reviewing a Pull Request on GitHub

### View PR Details

**With gh:**

```bash
gh pr view 123
gh pr diff 123
gh pr diff 123 --name-only
```

**With git + curl:**

```bash
PR_NUMBER=123

# Get PR details
curl -s \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER \
  | python3 -c "
import sys, json
pr = json.load(sys.stdin)
print(f\"Title: {pr['title']}\")
print(f\"Author: {pr['user']['login']}\")
print(f\"Branch: {pr['head']['ref']} -> {pr['base']['ref']}\")
print(f\"State: {pr['state']}\")
print(f\"Body:\n{pr['body']}\")"

# List changed files
curl -s \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER/files \
  | python3 -c "
import sys, json
for f in json.load(sys.stdin):
    print(f\"{f['status']:10} +{f['additions']:-4} -{f['deletions']:-4}  {f['filename']}\")"
```

### Check Out PR Locally for Full Review

This works with plain `git` — no `gh` needed:

```bash
# Fetch the PR branch and check it out
git fetch origin pull/123/head:pr-123
git checkout pr-123

# Now you can use read_file, search_files, run tests, etc.

# View diff against the base branch
git diff main...pr-123
```

**With gh (shortcut):**

```bash
gh pr checkout 123
```

### Leave Comments on a PR

**General PR comment — with gh:**

```bash
gh pr comment 123 --body "Overall looks good, a few suggestions below."
```

**General PR comment — with curl:**

```bash
curl -s -X POST \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/issues/$PR_NUMBER/comments \
  -d '{"body": "Overall looks good, a few suggestions below."}'
```

### Leave Inline Review Comments

**Single inline comment — with gh (via API):**

```bash
HEAD_SHA=$(gh pr view 123 --json headRefOid --jq '.headRefOid')

gh api repos/$OWNER/$REPO/pulls/123/comments \
  --method POST \
  -f body="This could be simplified with a list comprehension." \
  -f path="src/auth/login.py" \
  -f commit_id="$HEAD_SHA" \
  -f line=45 \
  -f side="RIGHT"
```

**Single inline comment — with curl:**

```bash
# Get the head commit SHA
HEAD_SHA=$(curl -s \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['head']['sha'])")

curl -s -X POST \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER/comments \
  -d "{
    \"body\": \"This could be simplified with a list comprehension.\",
    \"path\": \"src/auth/login.py\",
    \"commit_id\": \"$HEAD_SHA\",
    \"line\": 45,
    \"side\": \"RIGHT\"
  }"
```

### Submit a Formal Review (Approve / Request Changes)

**With gh:**

```bash
gh pr review 123 --approve --body "LGTM!"
gh pr review 123 --request-changes --body "See inline comments."
gh pr review 123 --comment --body "Some suggestions, nothing blocking."
```

**With curl — multi-comment review submitted atomically:**

```bash
HEAD_SHA=$(curl -s \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['head']['sha'])")

curl -s -X POST \
  -H "Authorization: token $GITHUB_TOKEN" \
  https://api.github.com/repos/$OWNER/$REPO/pulls/$PR_NUMBER/reviews \
  -d "{
    \"commit_id\": \"$HEAD_SHA\",
    \"event\": \"COMMENT\",
    \"body\": \"Code review from Hermes Agent\",
    \"comments\": [
      {\"path\": \"src/auth.py\", \"line\": 45, \"body\": \"Use parameterized queries to prevent SQL injection.\"},
      {\"path\": \"src/models/user.py\", \"line\": 23, \"body\": \"Hash passwords with bcrypt before storing.\"},
      {\"path\": \"tests/test_auth.py\", \"line\": 1, \"body\": \"Add test for expired token edge case.\"}
    ]
  }"
```

Event values: `"APPROVE"`, `"REQUEST_CHANGES"`, `"COMMENT"`

The `line` field refers to the line number in the *new* version of the file. For deleted lines, use `"side": "LEFT"`.

---

## 3. Review Checklist

When performing a code review (local or PR), systematically check:

### Correctness
- Does the code do what it claims?
- Edge cases handled (empty inputs, nulls, large data, concurrent access)?
- Error paths handled gracefully?

### Security
- No hardcoded secrets, credentials, or API keys
- Input validation on user-facing inputs
- No SQL injection, XSS, or path traversal
- Auth/authz checks where needed

### Code Quality
- Clear naming (variables, functions, classes)
- No unnecessary complexity or premature abstraction
- DRY — no duplicated logic that should be extracted
- Functions are focused (single responsibility)

### Testing
- New code paths tested?
- Happy path and error cases covered?
- Tests readable and maintainable?

### Performance
- No N+1 queries or unnecessary loops
- Appropriate caching where beneficial
- No blocking operations in async code paths

### Documentation
- Public APIs documented
- Non-obvious logic has comments explaining "why"