Re-checkout PR branch when there are local changes.

When a user commits local changes to a local branch (causing
`CheckoutMode.InvalidState`) and clicks "checkout to new branch", unmark
the current branch as a PR branch and check out a new branch.

Author: grokys

src/GitHub.App/Services/GitClient.cs

@@ -113,11 +113,20 @@ public Task SetTrackingBranch(IRepository repository, string branchName, string
             });
         }
 
-        public Task<Remote> GetHttpRemote(IRepository repo, string remote)
+        public Task UnsetConfig(IRepository repository, string key)
         {
+            Guard.ArgumentNotEmptyString(key, nameof(key));
+
             return Task.Factory.StartNew(() =>
             {
+                repository.Config.Unset(key);
+            });
+        }
 
+        public Task<Remote> GetHttpRemote(IRepository repo, string remote)
+        {
+            return Task.Factory.StartNew(() =>
+            {
                 var uri = GitService.GitServiceHelper.GetRemoteUri(repo, remote);
                 var remoteName = uri.IsHypertextTransferProtocol ? remote : remote + "-http";
                 var ret = repo.Network.Remotes[remoteName];

src/GitHub.App/Services/PullRequestService.cs

@@ -157,6 +157,17 @@ public IObservable<Unit> SwitchToBranch(ILocalRepositoryModel repository, int nu
             });
         }
 
+        public IObservable<Unit> UnmarkLocalBranch(ILocalRepositoryModel repository)
+        {
+            return Observable.Defer(async () =>
+            {
+                var repo = gitService.GetRepository(repository.LocalPath);
+                var configKey = $"branch.{repo.Head.FriendlyName}.ghfvs-pr";
+                await gitClient.UnsetConfig(repo, configKey);
+                return Observable.Return(Unit.Default);
+            });
+        }
+
         async Task DoFetchAndCheckout(ILocalRepositoryModel repository, int pullRequestNumber, string localBranchName)
         {
             var repo = gitService.GetRepository(repository.LocalPath);

src/GitHub.App/ViewModels/PullRequestDetailViewModel.cs

@@ -466,6 +466,12 @@ IObservable<Unit> DoCheckout(object unused)
                 case CheckoutMode.Switch:
                     operation = pullRequestsService.SwitchToBranch(repository, Number);
                     break;
+                case CheckoutMode.InvalidState:
+                    operation = pullRequestsService
+                        .UnmarkLocalBranch(repository)
+                        .SelectMany(_ => pullRequestsService.GetDefaultLocalBranchName(repository, Number, Title))
+                        .SelectMany(x => pullRequestsService.FetchAndCheckout(repository, Number, x));
+                    break;
                 default:
                     Debug.Fail("Invalid CheckoutMode in PullRequestDetailViewModel.DoCheckout.");
                     operation = Observable.Empty<Unit>();

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

@@ -69,6 +69,14 @@ public interface IGitClient
         /// <returns></returns>
         Task SetTrackingBranch(IRepository repository, string branchName, string remoteName);
 
+        /// <summary>
+        /// Unsets the configuration key in the local config.
+        /// </summary>
+        /// <param name="repository">The repository</param>
+        /// <param name="key">The configuration key. Keys are in the form 'section.name'.</param>
+        /// <returns></returns>
+        Task UnsetConfig(IRepository repository, string key);
+
         Task<Remote> GetHttpRemote(IRepository repo, string remote);
     }
 }

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

@@ -60,6 +60,13 @@ IObservable<IPullRequestModel> CreatePullRequest(IRepositoryHost host,
         /// <returns></returns>
         IObservable<HistoryDivergence> CalculateHistoryDivergence(ILocalRepositoryModel repository, int pullRequestNumber);
 
+        /// <summary>
+        /// Removes any association between the current branch and a pull request.
+        /// </summary>
+        /// <param name="repository">The repository.</param>
+        /// <returns></returns>
+        IObservable<Unit> UnmarkLocalBranch(ILocalRepositoryModel repository);
+
         IObservable<string> GetPullRequestTemplate(ILocalRepositoryModel repository);
     }
 }

src/UnitTests/GitHub.App/ViewModels/PullRequestDetailViewModelTests.cs

@@ -207,8 +207,7 @@ public async Task CheckoutNeedsPullShouldCallService()
 
             target.Item1.Checkout.Execute(null);
 
-            var unused = target.Item2.Received()
-                .FetchAndCheckout(Arg.Any<ILocalRepositoryModel>(), target.Item1.Number, "pr/123");
+            var unused = target.Item2.Received().FetchAndCheckout(Arg.Any<ILocalRepositoryModel>(), target.Item1.Number, "pr/123");
         }
 
         [Fact]
@@ -224,8 +223,7 @@ public async Task CheckoutSwitchShouldCallService()
 
             target.Item1.Checkout.Execute(null);
 
-            var unused = target.Item2.Received()
-                .SwitchToBranch(Arg.Any<ILocalRepositoryModel>(), 1);
+            var unused = target.Item2.Received().SwitchToBranch(Arg.Any<ILocalRepositoryModel>(), 1);
         }
 
         [Fact]
@@ -241,8 +239,28 @@ public async Task CheckoutFetchShouldCallService()
 
             target.Item1.Checkout.Execute(null);
 
-            var unused = target.Item2.Received()
-                .FetchAndCheckout(Arg.Any<ILocalRepositoryModel>(), target.Item1.Number, "pr/1-foo");
+            var unused = target.Item2.Received().FetchAndCheckout(Arg.Any<ILocalRepositoryModel>(), target.Item1.Number, "pr/1-foo");
+        }
+
+        [Fact]
+        public async Task CheckoutInvalidStateShouldCallService()
+        {
+            var target = CreateTargetAndService(
+                currentBranch: "pr/123",
+                existingPrBranch: "pr/123",
+                aheadBy: 1);
+
+            target.Item2.GetDefaultLocalBranchName(Arg.Any<ILocalRepositoryModel>(), 1, Arg.Any<string>())
+                .Returns(Observable.Return("pr/1-foo"));
+
+            await target.Item1.Load(CreatePullRequest(), new PullRequestFile[0]);
+
+            Assert.Equal(CheckoutMode.InvalidState, target.Item1.CheckoutMode);
+
+            target.Item1.Checkout.Execute(null);
+
+            var unused = target.Item2.Received().UnmarkLocalBranch(Arg.Any<ILocalRepositoryModel>());
+            unused = target.Item2.Received().FetchAndCheckout(Arg.Any<ILocalRepositoryModel>(), target.Item1.Number, "pr/1-foo");
         }
 
         PullRequestDetailViewModel CreateTarget(