style: Switch to nixfmt from nixpkgs-fmt

Most of the ecosystem has moved to this formatter,
and many people configured their editors to autoformat it with this formatter.

Closes: https://git.snix.dev/snix/snix/issues/62
Change-Id: Icf39e7836c91fc2ae49fbe22a40a639105bfb0bd
Reviewed-on: https://cl.snix.dev/c/snix/+/30671
Reviewed-by: Florian Klink <flokli@flokli.de>
Tested-by: besadii
Autosubmit: Ilan Joselevich <personal@ilanjoselevich.com>

nix/writeTree/default.nix

@@ -1,35 +1,55 @@
-{ depot, lib, pkgs, ... }:
+{
+  depot,
+  lib,
+  pkgs,
+  ...
+}:
 let
-  inherit (lib) fix pipe mapAttrsToList isAttrs concatLines isString isDerivation isPath;
+  inherit (lib)
+    fix
+    pipe
+    mapAttrsToList
+    isAttrs
+    concatLines
+    isString
+    isDerivation
+    isPath
+    ;
   inherit (depot.nix.utils) isReferencablePath;
 
-  esc = s: lib.escapeShellArg /* ensure paths import into store */ "${s}";
+  esc =
+    s:
+    lib.escapeShellArg # ensure paths import into store
+      "${s}";
 
-  writeTreeAtPath = path: tree:
+  writeTreeAtPath =
+    path: tree:
     ''
       mkdir -p "$out/"${esc path}
     ''
     + pipe tree [
-      (mapAttrsToList (k: v:
+      (mapAttrsToList (
+        k: v:
         if isReferencablePath v then
           "cp -R --reflink=auto ${esc "${v}"} \"$out/\"${esc path}/${esc k}"
         else if lib.isAttrs v then
           writeTreeAtPath (path + "/" + k) v
         else
-          throw "invalid type (expected path, derivation, string with context, or attrs)"))
+          throw "invalid type (expected path, derivation, string with context, or attrs)"
+      ))
       concatLines
     ];
 
-  /* Create a directory tree specified by a Nix attribute set structure.
+  /*
+    Create a directory tree specified by a Nix attribute set structure.
 
-     Each value in `tree` should either be a file, a directory, or another tree
-     attribute set. Those paths will be written to a directory tree
-     corresponding to the structure of the attribute set.
+    Each value in `tree` should either be a file, a directory, or another tree
+    attribute set. Those paths will be written to a directory tree
+    corresponding to the structure of the attribute set.
 
-     Type: string -> attrSet -> derivation
+    Type: string -> attrSet -> derivation
   */
-  writeTree = name: tree:
-    pkgs.runCommandLocal name { } (writeTreeAtPath "" tree);
+  writeTree = name: tree: pkgs.runCommandLocal name { } (writeTreeAtPath "" tree);
 in
 
 # __functor trick so readTree can add the tests attribute