Warn user when changes in local version of file

Warn if there have been chances to the target file between when the
permalink was created and the working copy.

Author: jcansdale

src/GitHub.App/Services/GitHubContextService.cs

@@ -14,6 +14,7 @@
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.TextManager.Interop;
+using LibGit2Sharp;
 
 namespace GitHub.App.Services
 {
@@ -340,6 +341,17 @@ public string ResolvePath(GitHubContext context)
             }
         }
 
+        public bool HasChangesInWorkingDirectory(string repositoryDir, string commitish, string path)
+        {
+            using (var repo = gitService.GetRepository(repositoryDir))
+            {
+                var commit = repo.Lookup<Commit>(commitish);
+                var paths = new[] { path };
+
+                return repo.Diff.Compare<Patch>(commit.Tree, DiffTargets.WorkingDirectory, paths).Count() > 0;
+            }
+        }
+
         static IEnumerable<(string commitish, string path)> ToObjectish(string treeishPath)
         {
             var index = 0;

src/GitHub.Exports/Services/IGitHubContextService.cs

@@ -15,5 +15,6 @@ public interface IGitHubContextService
         Uri ToRepositoryUrl(GitHubContext context);
         bool TryOpenFile(string repositoryDir, GitHubContext context);
         (string commitish, string path) ResolveGitObject(string repositoryDir, GitHubContext context);
+        bool HasChangesInWorkingDirectory(string repositoryDir, string commitish, string path);
     }
 }

src/GitHub.VisualStudio/Commands/OpenFromClipboardCommand.cs

@@ -13,6 +13,7 @@ public class OpenFromClipboardCommand : VsCommand<string>, IOpenFromClipboardCom
         public const string NoGitHubUrlMessage = "Couldn't a find a GitHub URL in clipboard";
         public const string NoResolveMessage = "Couldn't resolve Git object";
         public const string NoActiveRepositoryMessage = "There is no active repository to navigate";
+        public const string ChangesInWorkingDirectoryMessage = "This file has changed since the permalink was created";
 
         readonly Lazy<IGitHubContextService> gitHubContextService;
         readonly Lazy<ITeamExplorerContext> teamExplorerContext;
@@ -66,6 +67,12 @@ public override Task Execute(string url)
                 return Task.CompletedTask;
             }
 
+            var hasChanges = gitHubContextService.Value.HasChangesInWorkingDirectory(repositoryDir, commitish, path);
+            if (hasChanges)
+            {
+                vsServices.Value.ShowMessageBoxInfo(ChangesInWorkingDirectoryMessage);
+            }
+
             if (!gitHubContextService.Value.TryOpenFile(repositoryDir, context))
             {
                 // Couldn't open file

test/GitHub.VisualStudio.UnitTests/Commands/OpenFromClipboardCommandTests.cs

@@ -65,13 +65,48 @@ public async Task CouldResolve()
             vsServices.DidNotReceiveWithAnyArgs().ShowMessageBoxInfo(null);
         }
 
+        [Test]
+        public async Task NoChangesInWorkingDirectory()
+        {
+            var gitHubContextService = Substitute.For<IGitHubContextService>();
+            var context = new GitHubContext();
+            var repositoryDir = "repositoryDir";
+            var gitObject = ("master", "foo.cs");
+            var vsServices = Substitute.For<IVSServices>();
+            var target = CreateOpenFromClipboardCommand(gitHubContextService: gitHubContextService, vsServices: vsServices,
+                contextFromClipboard: context, repositoryDir: repositoryDir, gitObject: gitObject, hasChanges: false);
+
+            await target.Execute(null);
+
+            vsServices.DidNotReceiveWithAnyArgs().ShowMessageBoxInfo(null);
+            gitHubContextService.Received(1).TryOpenFile(repositoryDir, context);
+        }
+
+        [Test]
+        public async Task HasChangesInWorkingDirectory()
+        {
+            var gitHubContextService = Substitute.For<IGitHubContextService>();
+            var context = new GitHubContext();
+            var repositoryDir = "repositoryDir";
+            var gitObject = ("master", "foo.cs");
+            var vsServices = Substitute.For<IVSServices>();
+            var target = CreateOpenFromClipboardCommand(gitHubContextService: gitHubContextService, vsServices: vsServices,
+                contextFromClipboard: context, repositoryDir: repositoryDir, gitObject: gitObject, hasChanges: true);
+
+            await target.Execute(null);
+
+            vsServices.Received(1).ShowMessageBoxInfo(OpenFromClipboardCommand.ChangesInWorkingDirectoryMessage);
+            gitHubContextService.Received(1).TryOpenFile(repositoryDir, context);
+        }
+
         static OpenFromClipboardCommand CreateOpenFromClipboardCommand(
             IGitHubContextService gitHubContextService = null,
             ITeamExplorerContext teamExplorerContext = null,
             IVSServices vsServices = null,
             GitHubContext contextFromClipboard = null,
             string repositoryDir = null,
-            (string, string)? gitObject = null)
+            (string, string)? gitObject = null,
+            bool? hasChanges = null)
         {
             var sp = Substitute.For<IServiceProvider>();
             gitHubContextService = gitHubContextService ?? Substitute.For<IGitHubContextService>();
@@ -85,6 +120,11 @@ static OpenFromClipboardCommand CreateOpenFromClipboardCommand(
                 gitHubContextService.ResolveGitObject(repositoryDir, contextFromClipboard).Returns(gitObject.Value);
             }
 
+            if (hasChanges != null)
+            {
+                gitHubContextService.HasChangesInWorkingDirectory(repositoryDir, gitObject.Value.Item1, gitObject.Value.Item2).Returns(hasChanges.Value);
+            }
+
             return new OpenFromClipboardCommand(
                 new Lazy<IGitHubContextService>(() => gitHubContextService),
                 new Lazy<ITeamExplorerContext>(() => teamExplorerContext),