Add fetchGitMirror function

pkgs/bench6/default.nix

@@ -14,16 +14,19 @@
 , openblas
 , ovni
 , gitBranch ? "master"
-, gitURL ? "ssh://git@bscpm04.bsc.es/rarias/bench6.git"
 , gitCommit ? "bf29a53113737c3aa74d2fe3d55f59868faea7b4"
+, gitUrls ? [
+  "ssh://git@bscpm04.bsc.es/rarias/bench6.git"
+  "https://github.com/rodarima/bench6.git"
+]
 }:
 
 stdenv.mkDerivation rec {
   pname = "bench6";
   version = "${src.shortRev}";
 
-  src = builtins.fetchGit {
-    url = gitURL;
+  src = lib.fetchGitMirror {
+    urls = gitUrls;
     ref = gitBranch;
     rev = gitCommit;
   };