Add the install_file module from the steam deck config.

nix/configuration/configuration.nix

@@ -74,6 +74,7 @@
     ./roles/zfs
     ./roles/zrepl
     ./roles/zsh
+    ./util/install_files
     ./util/unfree_polyfill
   ];
 

nix/configuration/util/install_files/default.nix

@@ -0,0 +1,101 @@
+{
+  config,
+  lib,
+  pkgs,
+  home-manager,
+  ...
+}:
+
+let
+  inherit (lib)
+    filter
+    attrNames
+    ;
+in
+{
+  imports = [ ];
+
+  options.me = {
+    install.file = lib.mkOption {
+      type = lib.types.attrsOf (
+        lib.types.submodule (
+          { name, config, ... }:
+          {
+            options = {
+              enable = lib.mkOption {
+                type = lib.types.bool;
+                default = true;
+                defaultText = "me.install.file.‹name›.enable";
+                example = false;
+                description = "Whether we want to install this file.";
+              };
+              mode = lib.mkOption {
+                type = lib.types.str;
+                default = "0444";
+                defaultText = "me.install.file.‹name›.mode";
+                example = "0750";
+                description = "The read, write, execute permission flags.";
+              };
+              source = lib.mkOption {
+                type = lib.types.path;
+                defaultText = "me.install.file.‹name›.source";
+                example = ./files/foo.txt;
+                description = "The source file to install into the destination.";
+              };
+              target = lib.mkOption {
+                type = lib.types.str;
+                defaultText = "me.install.file.‹name›.target";
+                example = ".local/share/foo/bar.txt";
+                description = "The path where the file should be written.";
+              };
+            };
+
+            config = {
+              target = lib.mkDefault name;
+            };
+          }
+        )
+      );
+      defaultText = "me.install.file.‹name›";
+      default = { };
+      example = lib.literalExpression ''
+        {
+          ".config/foo/bar.txt" = {
+            source = ./files/bar.txt
+          };
+        }
+      '';
+    };
+  };
+
+  config = lib.mkMerge [
+    (lib.mkIf (config.me.install.file != { }) (
+      let
+        cfg = config.me.install.file;
+        install_file_targets = filter (target: config.me.install.file."${target}".enable) (attrNames cfg);
+      in
+      {
+        home.activation = {
+          installFiles = home-manager.lib.hm.dag.entryAfter [ "writeBoundary" ] (
+            let
+              install_commands = builtins.map (
+                target:
+                let
+                  target_config = config.me.install.file."${target}";
+                  source = lib.strings.escapeShellArg "${target_config.source}";
+                  destination = lib.strings.escapeShellArg target;
+                  mode = lib.strings.escapeShellArg "${target_config.mode}";
+                in
+                # $DRY_RUN_CMD ${pkgs.toyboy}/bin/install $VERBOSE_ARG -D -m ${mode} ${source} ${destination}
+                ''
+                  $DRY_RUN_CMD install $VERBOSE_ARG -D --compare -m ${mode} ${source} ${destination}
+                ''
+              ) install_file_targets;
+            in
+            (lib.strings.concatStringsSep "\n" install_commands)
+          );
+        };
+      }
+    ))
+  ];
+}