Resolve Race Condition in Pull RequestManager

[chidozieononiwu]

Occurs when a PR contains changes in multiple packages. Especially when those changes are made incrementally with multiple commits
Detect-API-Change step fires multiple calls to APIView for the various packages
One single package that does not have an existing pull request will cause the entire PR comment to be over written.

The issue starts at

azure-sdk-tools/src/dotnet/APIView/APIViewWeb/Managers/PullRequestManager.cs

Lines 73 to 89 in d784f16

	var pullRequestModel = await _pullRequestsRepository.GetPullRequestAsync(prNumber, repoName, packageName, language);
	if (pullRequestModel == null)
	{
	var repoInfo = repoName.Split("/");
	var pullRequest = await _githubClient.PullRequest.Get(repoInfo[0], repoInfo[1], prNumber);
	pullRequestModel = new PullRequestModel()
	{
	RepoName = repoName,
	PullRequestNumber = prNumber,
	FilePath = originalFile,
	CreatedBy = pullRequest.User.Login,
	PackageName = packageName,
	Language = language,
	Assignee = pullRequest.Assignee?.Login
	};
	}
	return pullRequestModel;

If no pullRequestModel is found for the package it will create a new pullRequestModel with no APIRevisionId (Line 78)

The presence of APIRevisionId determines if we fetch pullRequest information

azure-sdk-tools/src/dotnet/APIView/APIViewWeb/Controllers/PullRequestController.cs

Line 161 in d784f16

if (!string.IsNullOrEmpty(pullRequestModel.APIRevisionId))

Then we later check there is any pr info

azure-sdk-tools/src/dotnet/APIView/APIViewWeb/Managers/PullRequestManager.cs

Line 97 in d784f16

if (pullRequests.Count > 0)

This leads to all the packages in the PR being marked as having no changes even though its just one package

azure-sdk-tools/src/dotnet/APIView/APIViewWeb/Managers/PullRequestManager.cs

Lines 110 to 113 in d784f16

	else
	{
	bldr.Append(PR_APIVIEW_BOT_NO_CHANGE_COMMENT);
	}