Create flake config

flake.nix

@@ -0,0 +1,30 @@
+{
+  description = "A semi-verbose flake format helper.";
+
+  outputs = { self }:
+  let
+    inherit (builtins) elemAt foldl' head isAttrs length map zipAttrsWith;
+
+    # Copied from <nixpkgs/lib/attrsets.nix> to avoid taking a dependency
+    recursiveUpdateUntil = pred: lhs: rhs:
+      let f = attrPath:
+        zipAttrsWith (n: values:
+          let here = attrPath ++ [n];
+          in
+            if length values == 1 || pred here (elemAt values 1) (head values)
+            then head values
+            else f here values
+        );
+      in f [] [rhs lhs];
+    recursiveUpdate = lhs: rhs:
+      recursiveUpdateUntil (path: lhs: rhs: !(isAttrs lhs && isAttrs rhs)) lhs rhs;
+  in
+  {
+    /* Create the flake outputs for systems and merge them into the expected format.
+
+       system-outputs: function from a system to the flake outputs for that system.
+       systems: a list of systems to produce flake outputs for.
+    */
+    outputs-for = system-outputs: systems: foldl' recursiveUpdate {} (map system-outputs systems);
+  };
+}