Add GITHUB_API_BASE_URL environment variable

[cacapouh]

Enable integration with self-hosted GitHub Enterprise servers by allowing custom API base URL configuration through environment variable.

#96

[gemini-code-assist]

Hello @cacapouh, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

As gemini-code-assist, I've reviewed this pull request. The primary goal of this PR is to enhance the application's compatibility by allowing users to specify a custom GitHub API base URL. This is particularly useful for integrating with self-hosted GitHub Enterprise instances, which use a different API endpoint than the public https://api.github.com. The change is implemented by introducing a new environment variable, GITHUB_API_BASE_URL, which is then used in relevant API calls throughout the codebase, falling back to the default public URL if the variable is not set.

Highlights

• Environment Variable: Introduces the GITHUB_API_BASE_URL environment variable to allow users to specify their custom GitHub API endpoint.
• API URL Configuration: Updates code in both the Python backend and Next.js frontend to read and utilize the GITHUB_API_BASE_URL environment variable for constructing GitHub API request URLs.

Changelog

• api/data_pipeline.py
  • In the get_github_file_content function, the hardcoded GitHub API base URL (https://api.github.com) is replaced with a value retrieved from the GITHUB_API_BASE_URL environment variable using os.getenv, defaulting to the public API URL if the variable is not present (lines 446-447).
• src/app/[owner]/[repo]/page.tsx
  • A new constant apiBaseUrl is introduced to read the GITHUB_API_BASE_URL environment variable using process.env, defaulting to the public API URL (line 1060).
  • The API URL for fetching the repository tree (/git/trees) is updated to use the configurable apiBaseUrl (line 1062).
  • The API URL for fetching the README (/readme) is updated to use the configurable apiBaseUrl (line 1103).

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---

Env var sets the base,
GitHub Enterprise finds its place,
API calls flow.

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[gemini-code-assist]

Code Review

This pull request introduces a valuable feature by allowing the GitHub API base URL to be configured via the GITHUB_API_BASE_URL environment variable, which is great for supporting GitHub Enterprise instances.

The implementation in the TypeScript file (page.tsx) correctly handles the base URL construction. However, the Python implementation (data_pipeline.py) has a critical issue in how it constructs the final API URL, potentially leading to incorrect URLs, especially in the default case or when the provided base URL includes a scheme. Additionally, both implementations could be made more robust against trailing slashes in the provided base URL.

I've provided specific suggestions to address these points. It would also be beneficial to document how the GITHUB_API_BASE_URL environment variable should be formatted (e.g., including the scheme like https://my.ghe.server/api/v3) for users of this feature.

Summary of Findings

• Critical URL Construction Bug in Python: The Python code in api/data_pipeline.py incorrectly prepends https:// to the api_base_url when the default value or a user-provided value for GITHUB_API_BASE_URL already contains the scheme. This results in malformed URLs like https://https://api.github.com/....
• URL Robustness (Trailing Slashes): Both Python and TypeScript implementations could be improved to handle potential trailing slashes in the GITHUB_API_BASE_URL to prevent double slashes in the constructed API URLs (e.g., ...base//path/...).
• Environment Variable Usage in Next.js: The usage of process.env.GITHUB_API_BASE_URL in src/app/[owner]/[repo]/page.tsx is appropriate for React Server Components or server-side execution contexts in Next.js. This is not an issue but an observation confirming correct usage in its likely context.

Merge Readiness

This pull request introduces an important feature for GitHub Enterprise support. However, there's a critical issue in the Python code (api/data_pipeline.py) related to API URL construction that needs to be addressed before merging. Additionally, a medium-severity improvement for handling trailing slashes in the base URL is suggested for both Python and TypeScript implementations.

I recommend that these changes, particularly the critical one, be made before this PR is merged. As an AI reviewer, I am not authorized to approve pull requests; please ensure further review and approval by team members.

[gemini-code-assist]

The current construction of api_url has a couple of issues:

1. Critical: If GITHUB_API_BASE_URL is not set, api_base_url becomes "https://api.github.com". Then, api_url becomes f"https://https://api.github.com/...", which is incorrect due to the double https://.
2. Medium: If GITHUB_API_BASE_URL is set by the user and already includes the https:// scheme (e.g., "https://my.ghe.com/api/v3"), the same double https:// issue will occur.
3. Minor: If GITHUB_API_BASE_URL ends with a trailing slash (e.g., "https://my.ghe.com/api/v3/"), the resulting URL might have a double slash (e.g., "...v3//repos/..."), which is generally undesirable though often tolerated by servers.

Could we adjust the logic to ensure the GITHUB_API_BASE_URL is expected to contain the scheme, and then we don't prepend https://? Also, stripping any trailing slash from the base URL would make it more robust. For example:

Suggested change

	api_base_url = os.getenv("GITHUB_API_BASE_URL", "https://api.github.com")
	api_url = f"https://{api_base_url}/repos/{owner}/{repo}/contents/{file_path}"
	raw_github_api_base_url = os.getenv("GITHUB_API_BASE_URL", "https://api.github.com")
	# Ensure the base URL includes the scheme and remove any trailing slash for clean concatenation.
	api_base_url = raw_github_api_base_url.rstrip('/')
	api_url = f"{api_base_url}/repos/{owner}/{repo}/contents/{file_path}"

[gemini-code-assist]

The logic for apiBaseUrl is good in that it expects the full base URL (including scheme) from process.env.GITHUB_API_BASE_URL or defaults correctly.

To make it more robust, what do you think about ensuring that apiBaseUrl doesn't have a trailing slash? If process.env.GITHUB_API_BASE_URL is set to something like "https://my.ghe.com/api/v3/", the current concatenation apiUrl = ${apiBaseUrl}/repos/...would result in"https://my.ghe.com/api/v3//repos/..."`. While many servers handle // as /, it's cleaner to avoid it.

Consider removing a potential trailing slash:

        const apiBaseUrl = (process.env.GITHUB_API_BASE_URL || 'https://api.github.com').replace(/\/$/, '');