Adding warning message if branch already exists

src/UnityExtension/Assets/Editor/GitHub.Unity/UI/BranchesView.cs

@@ -16,9 +16,12 @@ namespace GitHub.Unity
         private const string ConfirmSwitchOK = "Switch";
         private const string ConfirmSwitchCancel = "Cancel";
         private const string ConfirmCheckoutBranchTitle = "Confirm branch checkout";
-        private const string ConfirmCheckoutBranchMessage = "Checkout branch {0}?";
+        private const string ConfirmCheckoutBranchMessage = "Checkout branch {0} from {1}?";
         private const string ConfirmCheckoutBranchOK = "Checkout";
         private const string ConfirmCheckoutBranchCancel = "Cancel";
+        private const string WarningCheckoutBranchExistsTitle = "Branch already exists";
+        private const string WarningCheckoutBranchExistsMessage = "Branch {0} already exists";
+        private const string WarningCheckoutBranchExistsOK = "Ok";
         private const string NewBranchCancelButton = "x";
         private const string NewBranchConfirmButton = "Create";
         private const string FavoritesSetting = "Favorites";
@@ -668,32 +671,53 @@ namespace GitHub.Unity
                                 .FinallyInUI((success, e) =>
                                 {
                                     if (success)
+                                    {
                                         Refresh();
+                                    }
                                     else
                                     {
                                         EditorUtility.DisplayDialog(Localization.SwitchBranchTitle,
                                             String.Format(Localization.SwitchBranchFailedDescription, node.Name),
-                                        Localization.Ok);
+                                            Localization.Ok);
                                     }
                                 }).Start();
                         }
                     }
                     else if (node.Type == NodeType.RemoteBranch)
                     {
-                        if (EditorUtility.DisplayDialog(ConfirmCheckoutBranchTitle, String.Format(ConfirmCheckoutBranchMessage, node.Name), ConfirmCheckoutBranchOK, ConfirmCheckoutBranchCancel))
+                        var indexOfFirstSlash = selectedNode.Name.IndexOf('/');
+                        var originName = selectedNode.Name.Substring(0, indexOfFirstSlash);
+                        var branchName = selectedNode.Name.Substring(indexOfFirstSlash + 1);
+
+                        if (Repository.LocalBranches.Any(localBranch => localBranch.Name == branchName))
                         {
-                            GitClient.CreateBranch(selectedNode.Name.Substring(selectedNode.Name.IndexOf('/') + 1), selectedNode.Name)
-                                .FinallyInUI((success, e) =>
-                                {
-                                    if (success)
-                                        Refresh();
-                                    else
+                            EditorUtility.DisplayDialog(WarningCheckoutBranchExistsTitle, 
+                                String.Format(WarningCheckoutBranchExistsMessage, branchName),
+                                WarningCheckoutBranchExistsOK);
+                        }
+                        else
+                        {
+                            var confirmCheckout = EditorUtility.DisplayDialog(ConfirmCheckoutBranchTitle, 
+                                String.Format(ConfirmCheckoutBranchMessage, node.Name, originName), 
+                                ConfirmCheckoutBranchOK, ConfirmCheckoutBranchCancel);
+
+                            if (confirmCheckout)
+                            {
+                                GitClient.CreateBranch(branchName, selectedNode.Name)
+                                    .FinallyInUI((success, e) =>
                                     {
-                                        EditorUtility.DisplayDialog(Localization.SwitchBranchTitle,
-                                            String.Format(Localization.SwitchBranchFailedDescription, node.Name),
-                                        Localization.Ok);
-                                    }
-                                }).Start();
+                                        if (success)
+                                        {
+                                            Refresh();
+                                        }
+                                        else
+                                        {
+                                            EditorUtility.DisplayDialog(Localization.SwitchBranchTitle,
+                                                String.Format(Localization.SwitchBranchFailedDescription, node.Name),
+                                                Localization.Ok);
+                                        }
+                                    }).Start();
+                            }
                         }
                     }
                 }