feat: introduce treefmt and fmt all

nix/default.nix

@@ -1,26 +1,34 @@
-{versionsPath}: let
+{ versionsPath }:
+let
   channelVersions = import versionsPath;
-  mkChannelSource = name: let
-    channelVersion = builtins.getAttr name channelVersions;
-  in
+  mkChannelSource =
+    name:
+    let
+      channelVersion = builtins.getAttr name channelVersions;
+    in
     builtins.fetchGit {
       # Descriptive name to make the store path easier to identify
       inherit name;
       inherit (channelVersion) url ref rev;
     };
-  nixPath = builtins.concatStringsSep ":" (builtins.map
-    (elemName: let
-      elem = builtins.getAttr elemName channelVersions;
-      elemPath = mkChannelSource elemName;
-      suffix =
-        if builtins.hasAttr "suffix" elem
-        then elem.suffix
-        else "";
-    in
-      builtins.concatStringsSep "=" [elemName elemPath] + suffix)
-    (builtins.attrNames channelVersions));
-  pkgs = import (mkChannelSource "nixpkgs") {};
-in {
+  nixPath = builtins.concatStringsSep ":" (
+    builtins.map (
+      elemName:
+      let
+        elem = builtins.getAttr elemName channelVersions;
+        elemPath = mkChannelSource elemName;
+        suffix = if builtins.hasAttr "suffix" elem then elem.suffix else "";
+      in
+      builtins.concatStringsSep "=" [
+        elemName
+        elemPath
+      ]
+      + suffix
+    ) (builtins.attrNames channelVersions)
+  );
+  pkgs = import (mkChannelSource "nixpkgs") { };
+in
+{
   inherit nixPath;
   channelSources = pkgs.writeText "channels.rc" ''
     export NIX_PATH=${nixPath}