building-github-index

What this skill does

# Building GitHub Index

Create markdown indexes of GitHub repositories optimized for Claude project knowledge. Indexes enable retrieval via GitHub API with semantic descriptions for effective matching.

## Quick Start

```bash
# Documentation repos (markdown/notebooks)
python scripts/github_index.py owner/repo -o index.md

# Code repos (extract symbols via tree-sitter)
python scripts/github_index.py owner/repo --code-symbols -o index.md

# Multiple repos combined
python scripts/github_index.py owner/repo1 owner/repo2 -o combined.md
```

## Script Options

| Flag | Description |
|------|-------------|
| `-o, --output` | Output file (default: `github_index.md`) |
| `--token` | GitHub PAT; also reads `GITHUB_TOKEN` env |
| `--include-patterns` | Only index matching globs: `"docs/**" "src/**"` |
| `--exclude-patterns` | Skip matching globs: `"test/**"` |
| `--max-files` | Cap files per repo (default: 200) |
| `--skip-fetch` | Tree only, no content fetch (fast, filename-only descriptions) |
| `--code-symbols` | Include code files, extract function/class names via tree-sitter |

## Description Extraction Priority

1. **YAML frontmatter** - `title:` and `description:` fields
2. **Markdown headings** - First h1/h2 as title, subsequent as topics
3. **Notebook cells** - First markdown cell heading
4. **Code symbols** - Public function/class names (with `--code-symbols`)
5. **Path-derived** - Convert filename to words (fallback)

## When Descriptions Fail

Some repos have stub files (links to external docs, empty readmes). In these cases:

**Manual curation recommended.** Use the tree output and domain knowledge:

```bash
# Get tree structure only (fast)
python scripts/github_index.py owner/repo --skip-fetch -o skeleton.md
# Then manually enhance descriptions based on domain knowledge
```

For code-heavy repos with embedded apps:
- Directory names encode purpose: `acc_wav_gen` → "ACC waveform generation"
- Peripheral acronyms map to functions: AFEC=ADC, MCAN=CAN, TWIHS=I2C
- Operation modes: blocking, interrupt, dma, polled

## Output Format

```markdown
# {Repo} - Content Index

**Repository:** {url}
**Branch:** `{branch}`

## Retrieval Method
{API curl commands}

---

## {Category}

| Description | Path |
|-------------|------|
| {What this covers} | `{path/file.md}` |
```

Description column leads (relevance matching), path follows (retrieval key).

## API Access

Enumerate files:
```bash
curl -sL "https://api.github.com/repos/OWNER/REPO/git/trees/BRANCH?recursive=1"
```

Fetch content:
```bash
curl -s "https://api.github.com/repos/OWNER/REPO/contents/PATH?ref=BRANCH" \
  -H "Accept: application/vnd.github+json" | \
  python3 -c "import sys,json,base64; print(base64.b64decode(json.load(sys.stdin)['content']).decode())"
```

## Network

Both scripts download a repo tarball (single HTTP request, no per-file rate limits) then process files locally. Allowlist: `api.github.com` (tarball redirects via this endpoint)

## Related Skills

- `accessing-github-repos` - Private repos, PAT setup, tarball download
- `mapping-codebases` - Detailed code structure (methods, imports, line numbers)

## Condensed Format (pk_index.py)

For token-constrained project knowledge, use the condensed script:

```bash
python scripts/pk_index.py owner/repo -o repo_pk.md
```

Produces ~80% smaller output:
- Single line per file: `path` — description
- Symbols only (no signatures)
- 15 files max per category
- No retrieval instructions section

Ideal when adding multiple repo indexes to project knowledge.