flake-parts/action-flake-update/default.nix

@@ -0,0 +1,24 @@
+{
+  perSystem =
+    { config
+    , pkgs
+    , ...
+    }:
+    let
+      name = builtins.baseNameOf ./.;
+      script = config.writers.writePureShellScriptBin
+        name
+        [
+          pkgs.bash
+          pkgs.coreutils
+          pkgs.git
+          pkgs.nix
+        ]
+        ''
+          bash ${./script.sh}
+        '';
+    in
+    {
+      packages.${name} = script;
+    };
+}

flake-parts/action-flake-update/script.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+COMMIT_MSG="update flake lock - $(date --iso-8601=minutes)"
+
+nix --experimental-features "nix-command flakes" \
+  flake update --commit-lock-file --commit-lockfile-summary "$COMMIT_MSG"