Use the Mastodon version from nixpkgs

README.md

@@ -2,6 +2,8 @@
 
 ## Installation notes
 
+0. Use the unstable channel.
+
 1. Prepare the new machine ([man nixos](https://nixos.org/manual/nixos/stable/#sec-installation))
 
 ```

mastodon.nix

@@ -7,7 +7,10 @@ let
     srcOverride = pkgs.applyPatches {
       src = pkgs.fetchgit {
         url = "https://github.com/mastodon/mastodon.git";
-        rev = "v4.1.0"; # "v${pkgs.mastodon.version}";
+        rev = "v${pkgs.mastodon.version}";
+        # sha256 mismatch will not allow automatic updates on every
+        # new Mastodon release. We don't want to have problems with
+        # updated dependencies in the unstable channel.
         sha256 = "sha256-a3EpeTQBCP+J4Gde/iixcg3VUhZbw4DwbZp8GDRAzAI=";
       };
       patches =  [