Don't let the same doctype be selectable twice in the Nested Content configuration

src/Umbraco.Web.UI.Client/src/views/propertyeditors/nestedcontent/nestedcontent.controller.js

@@ -37,6 +37,18 @@
             });
         });
 
+        $scope.selectableDocTypesFor = function (config) {
+            // return all doctypes that are:
+            // 1. either already selected for this config, or
+            // 2. not selected in any other config
+            return _.filter($scope.model.docTypes, function (docType) {
+                return docType.alias === config.ncAlias || !_.find($scope.model.value, function(c) {
+                    return docType.alias === c.ncAlias;
+                });
+            });
+
+        }
+
         if (!$scope.model.value) {
             $scope.model.value = [];
             $scope.add();

src/Umbraco.Web.UI.Client/src/views/propertyeditors/nestedcontent/nestedcontent.doctypepicker.html

@@ -22,7 +22,7 @@
                     </td>
                     <td>
                         <select id="{{model.alias}}_doctype_select"
-                            ng-options="dt.alias as dt.name for dt in model.docTypes | orderBy: 'name'"
+                            ng-options="dt.alias as dt.name for dt in selectableDocTypesFor(config) | orderBy: 'name'"
                             ng-model="config.ncAlias" required></select>
                     </td>
                     <td>