Confirmation box for when adding multiple folders on the same path (#1960)

gui/default/syncthing/core/pathIsSubDirDirective.js

@@ -0,0 +1,36 @@
+angular.module('syncthing.core')
+    .directive('pathIsSubDir', function () {
+        return {
+            require: 'ngModel',
+            link: function (scope, elm, attrs, ctrl) {
+                ctrl.$parsers.unshift(function (viewValue) {
+                    // This function checks whether xdir is a subdirectory of ydir,
+                    // e.g. it would return true if xdir = "/home/a", ydir = "/home/a/b".
+                    function isSubDir(xdir, ydir) {
+                        var xdirArr = xdir.split(scope.system.pathSeparator);
+                        var ydirArr = ydir.split(scope.system.pathSeparator);
+                        if (xdirArr.slice(-1).pop() === "") {
+                            xdirArr = xdirArr.slice(0, -1);
+                        }
+                        if (xdirArr.length > ydirArr.length) {
+                            return false;
+                        }
+                        return xdirArr.map(function(e, i) {
+                            return xdirArr[i] === ydirArr[i];
+                        }).every(function(e) { return e });
+                    }
+
+                    scope.pathIsSubFolder = false;
+                    scope.otherFolder = "";
+                    for (var folderID in scope.folders) {
+                        if (isSubDir(scope.folders[folderID].path, viewValue)) {
+                            scope.otherFolder = folderID;
+                            scope.pathIsSubFolder = true;
+                            break;
+                        }
+                    }
+                    return viewValue;
+                });
+            }
+        };
+});