Update PRs with VS information when inserted.

[JoeRobich]

We can create an Azure pipeline that is triggered when the VS repo is updated. This pipeline can look for updates to our inserted components in the latest merge. If we detect that we have inserted updated components, we can take the current build and previous inserted build to get a range of commits from the repo that was inserted. We can then determine the PRs that were merged and can post comments to them that the change has inserted into VS.

Possible ways to trigger:

1. We can trigger off merges into the VS repo
2. We can trigger off successful VS builds

How to determine PRs to update:

1. Get the current component build #
2. Get the previous component build # from git
3. Locate those builds with AzDO apis

   roslyn-tools/src/RoslynInsertionTool/RoslynInsertionTool/RoslynInsertionTool.VisualStudioTeamServices.cs

   Line 321 in 0e3e6f4

   private static async Task<Build> GetSpecificComponentBuildAsync(BuildVersion version, CancellationToken cancellationToken)

4. Get the Git commits between builds

   roslyn-tools/src/RoslynInsertionTool/RoslynInsertionTool/RoslynInsertionTool.VisualStudioTeamServices.cs

   Line 484 in 0e3e6f4

   internal static async Task<(List<GitCommit> changes, string diffLink)> GetChangesBetweenBuildsAsync(Build fromBuild, Build tobuild, CancellationToken cancellationToken)

5. Use our merge PR log heuristics to find the PRs

   roslyn-tools/src/RoslynInsertionTool/RoslynInsertionTool/RoslynInsertionTool.VisualStudioTeamServices.cs

   Lines 604 to 611 in 0e3e6f4

   	if (oldBuild.Repository.Type == "GitHub" || !string.IsNullOrEmpty(Options.ComponentGitHubRepoName))
   	{
   	AppendGitHubChangesToDescription(changes, hardLimit, description, repoId);
   	}
   	else if (oldBuild.Repository.Type == "TfsGit")
   	{
   	AppendAzDOChangesToDescription(oldBuild, changes, hardLimit, description);
   	}

6. Post comments to PRs

   roslyn-tools/src/GithubMergeTool/GithubMergeTool.cs

   Lines 380 to 385 in 0e3e6f4

   	Task<HttpResponseMessage> PostComment(string prNumber, string comment)
   	{
   	// https://developer.github.com/v3/pulls/comments/#create-a-comment
   	var body = JsonConvert.SerializeObject(new { body = comment });
   	return _client.PostAsyncAsJson($"repos/{repoOwner}/{repoName}/issues/{prNumber}/comments", body);
   	}

What information do we want to add to PRs?

• Link to VS insertion PR
• If we trigger off VS build we could include minimum VS version for the change
• more??

Potentially this one pipeline could work for many teams if we develop a suitable config. Configuration may need to include Team Name, Component Name, Build Pipeline, Repo Url, additional information...