formatter: use a different treefmt root (#6792)

* formatter: use a different treefmt root

Problem: i use jujutsu as a VCS these days https://jj-vcs.github.io/jj/
and when using jujutsu workspaces, they dont contain the `.git`
file/folder that git worktrees have.

solution: use a different (unique) root file. I first tried with flake.nix for instnace but we have several in the tree while is only one "release.json"

* Update flake.nix

Co-authored-by: Austin Horstman <[email protected]>

---------

Co-authored-by: Austin Horstman <[email protected]>

Author: teto

flake.nix

@@ -48,7 +48,14 @@
         forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
       in
       {
-        formatter = forAllSystems (system: nixpkgs.legacyPackages.${system}.nixfmt-tree);
+        formatter = forAllSystems (
+          system:
+          nixpkgs.legacyPackages.${system}.nixfmt-tree.override {
+            settings = {
+              tree-root-file = "release.json";
+            };
+          }
+        );
 
         packages = forAllSystems (
           system: