got overlays working, patches next

overlays/blanket.nix

@@ -0,0 +1,11 @@
+final: prev: {
+  blanket = prev.blanket.overrideAttrs (old: rec {
+    version = "0.7.0";
+    src = prev.fetchFromGitHub {
+      owner = "rafaelmardojai";
+      repo = "blanket";
+      rev = "refs/tags/${version}";
+      sha256 = "sha256-mY7c5i0me7mMbD8c6eGJeaZpR8XI5QVL4n3M+j15Z1c=";
+    };
+  });
+}

overlays/gnome.nix

@@ -0,0 +1,14 @@
+final: prev:
+
+{
+  gnome = prev.gnome.overrideScope' (gnomeFinal: gnomePrev: {
+    mutter = gnomePrev.mutter.overrideAttrs (old: {
+      src = prev.pkgs.fetchgit {
+        url = "https://gitlab.gnome.org/vanvugt/mutter.git";
+        # GNOME 45: triple-buffering-v4-45
+        rev = "0b896518b2028d9c4d6ea44806d093fd33793689";
+        sha256 = "sha256-mzNy5GPlB2qkI2KEAErJQzO//uo8yO0kPQUwvGDwR4w=";
+      };
+    });
+  });
+}