Display PR review comments inline.

[grokys]

When the user clicks a review comment represented by a PullRequestReviewFileCommentViewModel, open the comment inline in a diff view:

This also handles showing outdated comments in a diff representing the commit at which the comment was left. Doing this required a few changes to the inline comment/PR session manager classes to make them accept a commit SHA instead of just assuming that the PR head will be needed.

Depends on #1545
Part of #1491

[meaghanlewis]

@grokys one thing I found interesting is that I couldn't get a diff view (the 3rd one) to open while reviewing comments.

[meaghanlewis]

I also found it interesting that for comment reviews, the comment is displayed as a Description versus comments or outdated comments. Could comment reviews just be called comments?

[grokys]

I think this is because there are two separate concepts here:

1. A comment on a line of code. These will be displayed under Comments or Outdated Comments. Using the web interface, these comments are left like so:

2. The comment attached to the review itself. This is what is displayed under Description:

[meaghanlewis]

Cool, thanks for clarifying the description comments @grokys.

The only other interesting thing was that a diff didn't open for one comment (I pointed out a few days ago. The example comes from PR 1492). I initially thought it had to do with the file extension, but don't think that's the case. I noticed that the diff I want to open isn't rendered by default in dotcom:

So I'm thinking that diff won't open because it's just a really large diff. Don't know how commonly this happens but might be worth it to show something in VS to indicate why the diff doesn't open.

[drguthals]

This also handles showing outdated comments in a diff representing the commit at which the comment was left.

Can you clarify this?

I have a ton of reviews/comments on this one file:

But I don't see any differentiation between outdated and new reviews? Not in that view above or in the comments:

However, it is working, when I click on a comment in the review in the pane it opens it up in the diff view.

Two things that might be out of scope or things we cannot fix:

1. Each time I click a comment the entire diff view reloads, is that expected?
2. When I click on the comment, if it is in a thread of comments for that line, there is no indication of this. Maybe we don't want one, but it was just interesting that I had to search through to find it. That being said, it might make sense for that functionality.