Using Copilot to explore a codebase

GitHub Copilot Chat can help you gain an understanding of the content, structure, and functionality of a codebase.

In this article

Introduction

If you've been assigned to work on a project that you're not familiar with—or you've found an interesting open source project that you want to contribute to—you'll need some understanding of the codebase before you can start making changes. This guide will show you how to use GitHub Copilot Chat to explore a codebase and quickly learn about the project.

Working with Copilot Chat

Throughout this guide, we'll work on GitHub.com, using Copilot Chat in assistive mode, which displays a Copilot Chat panel over the bottom right corner of your current page on GitHub.com.

You can expand the Copilot Chat panel, to give more space for displaying Copilot's responses, by clicking and dragging the edges of the panel.

Using the predefined prompts

Copilot Chat comes with a set of predefined prompts that can help you get started with exploring a codebase. You can use the prompts by clicking a button in the chat panel. The buttons are displayed when you start a new conversation with Copilot Chat. The selection of prompts varies depending on the currently displayed page on GitHub.com.

  1. Open the repository you want to explore on GitHub.com.

  2. Click the Code tab to display the main page of the repository.

  3. Press Shift+C to open Copilot Chat in assistive mode.

  4. Click the Tell me about this repository button in the chat panel.

    Screenshot of the chat panel with the 'Tell me about this repository' button highlighted.

    Tip

    If this button is not displayed, make sure you are on the main page of the repository and click the plus sign () at the top right of the Copilot panel to start a new conversation.

    A predefined prompt is submitted to Copilot and the response is displayed in the chat panel.

  5. Optionally, after reading the response, click the plus sign () at the top right of the Copilot panel to start a new conversation, then click How to get started with this repository.

Example prompts

The following prompts are examples of the kind of questions you can ask Copilot to help you find out about a codebase.

General questions

  • Based on the code in this repository, give me an overview of the architecture of the codebase. Provide evidence.

  • Which languages are used in this repo? Show the percentages for each language.

  • What are the core algorithms implemented in this repo?

  • What design patterns are used in this repository? Give a brief explanation of each pattern that you find, and an example of code from this repository that uses the pattern, with a link to the file.

Specific questions

Whether these questions are useful will depend on the codebase you're exploring.

  • How do I build this project?

  • Where is authentication handled in this codebase?

  • Analyze the code in this repository and tell me about the entry points for this application.

  • Describe the data flow in this application.

  • Analyze the code in this repository and tell me what application-level security mechanisms are employed. Provide references.

Understanding the files in a directory

Use Copilot to help you understand the purpose of the files in a directory, or individual files.

To find out about the files in a directory:

  1. Navigate to the directory on GitHub.com.
  2. Press Shift+C to open Copilot Chat in assistive mode.
  3. Ask Copilot: Explain the files in this directory.

To find out about a specific file:

  1. Open the file on GitHub.com.
  2. Press Shift+C to open Copilot Chat in assistive mode.
  3. For a small file, ask Copilot: Explain this file.
  4. For a large file, ask: Explain what this file does. Start with an overview of the purpose of the file. Then, in appropriately headed sections, go through each part of the file and explain what it does in detail.

Understanding specific lines of code

Use Copilot to help you understand specific lines of code in a file.

To find out about a specific line of code:

  1. On GitHub, navigate to a repository and open a file.
  2. Select the lines by clicking the line number for the first line you want to select, holding down Shift and clicking the line number for the last line you want to select.
  3. To ask your own question about the selected lines, click the Copilot icon () to the right of your selection. This displays the GitHub Copilot Chat panel with the selected lines indicated as the context of your question.
  4. To ask a predefined question, click the downward-pointing button beside the Copilot icon, then choose one of the options.

Screenshot of the Copilot buttons, highlighted with a dark orange outline, to the right of some selected code.

  1. If you clicked the Copilot icon, type a question in the prompt box at the bottom of the chat panel and press Enter.

Understanding a specific file or symbol

Use Copilot to help you understand the purpose of a specific file or symbol in the codebase. A symbol is a named entity in the code, such as a function, class, or variable.

  1. Navigate to a repository on GitHub.

  2. At the top right of the page, click next to the icon, then click Assistive to open the Copilot Chat panel.

  3. In the prompt box, click Attach, then click Files, folders, and symbols.

  4. Search for and select one or more files, folders, or symbols.

  5. In the prompt box, type a question and press Enter.

    Copilot replies in the chat panel.

    Tip

    Copilot's ability to answer natural language questions like these in a repository context is optimized when the semantic code search index for the repository is up to date. For more information, see Indexing repositories for Copilot Chat.

Finding out about commits

One good way to familiarize yourself with a project is to look at the recent work that's been happening. You can do this by browsing the recent commits.

  1. On GitHub, navigate to the main page of the repository.

  2. On the main page of the repository, above the file list, click commits.

    Screenshot of the main page for a repository. A clock icon and "178 commits" is highlighted with an orange outline.

  3. Click a commit message to display a diff view for that commit.

  4. In the Copilot Chat panel, enter: What does this commit do?.

  5. If necessary, you can follow up by entering: Explain in more detail.

Using the Insights tab

In addition to using Copilot to help you become familiar with a project, you can also use the Insights tab on GitHub.com. This gives you a high-level overview of the repository.

For more information, see Using Pulse to view a summary of repository activity and Viewing a project's contributors.

Further reading