Fix 403 errors when downloading metadata from Packagist and GitHub (ReactDownloader headers issue)

[pejman-hkh]

While using Repman as a proxy, we are encountering 403 Forbidden errors when downloading package files and metadata.

The issue appears to be related to missing or incorrect HTTP headers in ReactDownloader.php.

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Problem Details

1. Packagist returns 403 when the Repman header is sent.
2. GitHub returns 403 when no User-Agent header is provided.

Currently, the stream context does not properly adjust headers depending on the target host.

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Suggested Improvement

It would be better to conditionally set headers based on the request URL.

Example:

private function createContext(array $headers = [], string $url = '')
{
    if ($url && str_contains($url, 'github.com')) {
        $headers[] = 'User-Agent: MyApp';
    }

    $context = [
        'http' => [
            'header' => implode("\r\n", $headers),
            'follow_location' => 1,
            'max_redirects' => 20,
        ],
    ];

    return stream_context_create($context);
}

This approach:

• Ensures a valid User-Agent header for GitHub requests
• Avoids problematic headers when requesting from Packagist
• Prevents 403 errors during metadata and package downloads

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Why This Matters

Without proper header handling:

• GitHub blocks requests without User-Agent
• Packagist may block requests with certain custom headers
• Metadata downloads and dependency resolution can fail

If needed, I can prepare a pull request implementing this change.