add repoOverrides option

README.md

@@ -350,6 +350,26 @@ with pkgs.lib;
 }
 ```
 
+## Overriding repositories
+
+You can override repositories using `repoOverrides` argument.
+This allows to test changes before publishing.
+
+```
+{
+  packageOverrides = pkgs: {
+    nur = import (builtins.fetchTarball "https://github.com/nix-community/NUR/archive/master.tar.gz") {
+      inherit pkgs;
+      repoOverrides = {
+        mic92 = import ../nur-packages;
+        ## remote locations are also possible:
+        # mic92 = import (builtins.fetchTarball "https://github.com/your-user/nur-packages/archive/master.tar.gz");
+      };
+    };
+  };
+}
+```
+
 ## Contribution guideline
 
 - When adding packages to your repository make sure they build and set

default.nix

@@ -1,6 +1,8 @@
 { nurpkgs ? import <nixpkgs> {} # For nixpkgs dependencies used by NUR itself
   # Dependencies to call NUR repos with
-, pkgs ? null }:
+, pkgs ? null
+, repoOverrides ? { }
+}:
 
 let
   manifest = (builtins.fromJSON (builtins.readFile ./repos.json)).repos;
@@ -20,6 +22,6 @@ let
   };
 
 in {
-  repos =  lib.mapAttrs createRepo manifest;
+  repos =  (lib.mapAttrs createRepo manifest) // repoOverrides;
   repo-sources = lib.mapAttrs repoSource manifest;
 }