calchiwo/ExplainThisRepo ? reverse-engineered prompt

Build me a command line tool that helps me understand an unfamiliar codebase fast.

I want to give it a GitHub repo link, a local folder, or even a single file, and have it analyze the real signals in the project like configs, entry points, manifests, dependencies, and important high signal files. It should then create a clear EXPLAIN.md in the current folder, or print a short summary in the terminal, so I can quickly see what the repo does, how it is organized, where to start, and what I can ignore.

Please include a quick mode, a simple mode, and a detailed mode, plus a stack summary and a repo map. It should work with private repos too if I set up a GitHub token, and it should support choosing an LLM provider like OpenAI, Anthropic, Gemini, Ollama, Groq, or OpenRouter. If you need to look up current docs online while building it, go ahead.