nix: fix #126

* Update the readme to pull from cachix first, so users don't have to
  build nix.
* Pull `nixFlakes` from override for slightly newer ui, and consistency
  for users who change the nixos flake ref to something newer.

doc/start/index.md

@@ -4,6 +4,8 @@ The only dependency is nix, so make sure you have it [installed][install-nix].
 ## Get the Template
 Here is a snippet that will get you the template without the git history:
 ```sh
+nix-shell -p cachix --run cachix use nrdxp
+
 nix-shell https://github.com/nrdxp/nixflk/archive/core.tar.gz -A shell \
   --run "flk get core"
 
@@ -14,8 +16,6 @@ nix-shell
 git init
 git add .
 git commit -m init
-
-cachix use nrdxp
 ```
 
 This will place you in a new folder named `flk` with git initialized, and a
@@ -29,6 +29,8 @@ In addition, the [binary cache](../../cachix) is added for faster deployment.
 >   in the call to `flk get`
 > - Flakes ignore files that have not been added to git, so be sure to stage new
 >   files before building the system.
+> - You can choose to simply clone the repo with git if you want to follow
+>   upstream changes.
 
 ## Next Steps:
 - [Make installable ISO](./iso.md)

overlays/nixFlakes.nix

@@ -1,7 +1,11 @@
 final: prev: {
   nixFlakes = prev.nixFlakes.overrideAttrs
-    (self: {
+    (self:
-      patches = [
+      let
+        oldPatches = self.patches or [ ];
+      in
+      {
+        patches = oldPatches ++ [
           ../pkgs/tools/package-management/nix/0001-nix-command-and-flakes-by-default.patch
         ];
       });

overrides/default.nix

@@ -14,6 +14,7 @@
       element-desktop
       manix
       nixpkgs-fmt
+      nixFlakes
       qutebrowser
       signal-desktop
       starship;