Make compare view editable.

Make PR file compare view editable if PR branch is checked out.

Author: grokys

src/GitHub.App/SampleData/PullRequestDetailViewModelDesigner.cs

@@ -70,6 +70,7 @@ public PullRequestDetailViewModelDesigner()
         public IPullRequestModel Model { get; }
         public string SourceBranchDisplayName { get; set; }
         public string TargetBranchDisplayName { get; set; }
+        public bool IsCheckedOut { get; }
         public bool IsFromFork { get; }
         public string Body { get; }
         public IReactiveList<IPullRequestChangeNode> ChangedFilesTree { get; }

src/GitHub.App/Services/PullRequestService.cs

@@ -287,7 +287,8 @@ public IObservable<Tuple<string, string>> ExtractDiffFiles(
             IModelService modelService,
             IPullRequestModel pullRequest,
             string fileName,
-            string fileSha)
+            string fileSha,
+            bool isPullRequestBranchCheckedOut)
         {
             return Observable.Defer(async () =>
             {
@@ -300,7 +301,9 @@ public IObservable<Tuple<string, string>> ExtractDiffFiles(
 
                 // The right file - if it comes from a fork - may not be fetched so fall back to
                 // getting the file contents from the model service.
-                var right = await GetFileFromRepositoryOrApi(repository, repo, modelService, pullRequest.Head.Sha, fileName, fileSha);
+                var right = isPullRequestBranchCheckedOut ?
+                    Path.Combine(repository.LocalPath, fileName) :
+                    await GetFileFromRepositoryOrApi(repository, repo, modelService, pullRequest.Head.Sha, fileName, fileSha);
 
                 if (left == null)
                 {

src/GitHub.App/ViewModels/PullRequestDetailViewModel.cs

@@ -358,7 +358,7 @@ public async Task Load(IPullRequestModel pullRequest)
         public Task<Tuple<string, string>> ExtractDiffFiles(IPullRequestFileNode file)
         {
             var path = Path.Combine(file.DirectoryPath, file.FileName);
-            return pullRequestsService.ExtractDiffFiles(repository, modelService, model, path, file.Sha).ToTask();
+            return pullRequestsService.ExtractDiffFiles(repository, modelService, model, path, file.Sha, IsCheckedOut).ToTask();
         }
 
         /// <summary>

src/GitHub.Exports.Reactive/Services/IPullRequestService.cs

@@ -120,13 +120,18 @@ IObservable<string> ExtractFile(
         /// <param name="pullRequest">The pull request details.</param>
         /// <param name="fileName">The filename relative to the repository root.</param>
         /// <param name="fileSha">The SHA of the file in the pull request.</param>
-        /// <returns>The filenames of the left and right files for the diff.</returns>
+        /// <param name="isPullRequestBranchCheckedOut">
+        /// Whether the pull request branch is currently checked out. If so the right file returned
+        /// will be the path to the file in the working directory.
+        /// </param>
+        /// <returns>The paths of the left and right files for the diff.</returns>
         IObservable<Tuple<string, string>> ExtractDiffFiles(
             ILocalRepositoryModel repository,
             IModelService modelService,
             IPullRequestModel pullRequest,
             string fileName,
-            string fileSha);
+            string fileSha,
+            bool isPullRequestBranchCheckedOut);
 
         /// <summary>
         /// Remotes all unused remotes that were created by GitHub for Visual Studio to track PRs

src/GitHub.Exports.Reactive/ViewModels/IPullRequestDetailViewModel.cs

@@ -79,6 +79,11 @@ public interface IPullRequestDetailViewModel : IViewModel, IHasBusy
         /// </summary>
         string TargetBranchDisplayName { get; }
 
+        /// <summary>
+        /// Gets a value indicating whether the pull request branch is checked out.
+        /// </summary>
+        bool IsCheckedOut { get; }
+
         /// <summary>
         /// Gets a value indicating whether the pull request comes from a fork.
         /// </summary>

src/GitHub.VisualStudio/UI/Views/PullRequestDetailView.xaml.cs

@@ -87,19 +87,24 @@ async Task DoDiffFile(IPullRequestFileNode file)
                 var rightLabel = $"{file.FileName};PR {ViewModel.Model.Number}";
                 var caption = $"Diff - {file.FileName}";
                 var tooltip = $"{leftLabel}\nvs.\n{rightLabel}";
+                var options = __VSDIFFSERVICEOPTIONS.VSDIFFOPT_DetectBinaryFiles |
+                    __VSDIFFSERVICEOPTIONS.VSDIFFOPT_LeftFileIsTemporary;
+
+                if (!ViewModel.IsCheckedOut)
+                {
+                    options |= __VSDIFFSERVICEOPTIONS.VSDIFFOPT_RightFileIsTemporary;
+                }
 
                 Services.DifferenceService.OpenComparisonWindow2(
-                fileNames.Item1,
-                fileNames.Item2,
-                caption,
-                tooltip,
-                leftLabel,
-                rightLabel,
-                string.Empty,
-                string.Empty,
-                (int)(__VSDIFFSERVICEOPTIONS.VSDIFFOPT_DetectBinaryFiles |
-                    __VSDIFFSERVICEOPTIONS.VSDIFFOPT_LeftFileIsTemporary |
-                    __VSDIFFSERVICEOPTIONS.VSDIFFOPT_RightFileIsTemporary));
+                    fileNames.Item1,
+                    fileNames.Item2,
+                    caption,
+                    tooltip,
+                    leftLabel,
+                    rightLabel,
+                    string.Empty,
+                    string.Empty,
+                    (uint)options);
             }
             catch (Exception e)
             {