Allow external link on the navigation area.

modules/docs/src/Volo.Docs.Web/Areas/Documents/Helpers/TagHelpers/TreeTagHelper.cs

@@ -116,6 +116,11 @@ namespace Volo.Docs.Areas.Documents.Helpers.TagHelpers
 
         private string NormalizePath(string path, bool hasChildItems)
         {
+            if (IsExternalLink(path))
+            {
+                return path;
+            }
+
             var pathWithoutFileExtension = RemoveFileExtensionFromPath(path);
 
             if (string.IsNullOrWhiteSpace(path))
@@ -126,6 +131,16 @@ namespace Volo.Docs.Areas.Documents.Helpers.TagHelpers
             return  "/documents/" + ProjectName + "/" + Version + "/" + pathWithoutFileExtension;
         }
 
+        protected virtual bool IsExternalLink(string path)
+        {
+            if (path.IsNullOrEmpty())
+            {
+                return false;
+            }
+
+            return path.StartsWith("http") || path.StartsWith("https");
+        }
+
         private string RemoveFileExtensionFromPath(string path)
         {
             if (path == null)
@@ -137,6 +152,5 @@ namespace Volo.Docs.Areas.Documents.Helpers.TagHelpers
                  ? path.Left(path.Length - ProjectFormat.Length - 1)
                  : path;
         }
-
     }
 }