Use GraphQL to collect eng/common from GitHub

[premun]

#4751

[Copilot]

Pull Request Overview

This PR migrates GitHub file retrieval to use GraphQL, reducing rate limiting issues and improving performance. Key changes include:

• Removing legacy caching and abuse retry tests.
• Removing memory cache support from RemoteRepoBase and adjusting dependent constructors.
• Updating GitHubClient to perform file retrieval via GraphQL with added logging and caching.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/Microsoft.DotNet.DarcLib.Tests/GitHubClientTests.cs	Removed tests for caching and abuse exception retry scenarios
src/Microsoft.DotNet.Darc/DarcLib/RemoteRepoBase.cs	Removed memory cache parameter and property to simplify repository access
src/Microsoft.DotNet.Darc/DarcLib/LocalLibGit2Client.cs	Added error handling around file mode conversion with improved logging
src/Microsoft.DotNet.Darc/DarcLib/Helpers/GitFile.cs	Updated newline logic for content normalization
src/Microsoft.DotNet.Darc/DarcLib/GitHubClient.cs	Implemented GraphQL query execution with caching and improved error handling
src/Microsoft.DotNet.Darc/DarcLib/AzureDevOpsClient.cs	Adjusted base constructor call to reflect changes in caching support

Comments suppressed due to low confidence (1)

test/Microsoft.DotNet.DarcLib.Tests/GitHubClientTests.cs:191

• The removal of caching and abuse exception tests reduces test coverage for key scenarios. Please ensure that the new GraphQL integration is adequately tested.

[TestCase(true)]

[Copilot]

The log message placeholder '{ilePath}' appears to be a typo. Consider updating it to '{filePath}' for clarity.

Suggested change

	_logger.LogError("Failed to parse file mode {mode} for file {ilePath}", file.Mode, file.FilePath);
	_logger.LogError("Failed to parse file mode {mode} for file {filePath}", file.Mode, file.FilePath);

[Copilot]

Creating a new HttpClient instance for every GraphQL query may lead to socket exhaustion. Consider using IHttpClientFactory or reusing a shared HttpClient instance.

Suggested change

	using var client = new HttpClient();
	client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
	client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
	client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("DarcLib", DarcLibVersion));
	_httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
	_httpClient.DefaultRequestHeaders.UserAgent.Clear();
	_httpClient.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("DarcLib", DarcLibVersion));