add ssh agent

nixos/configuration.nix

@@ -1,7 +1,12 @@
 # Edit this configuration file to define what should be installed on
 # your system.  Help is available in the configuration.nix(5) man page
 # and in the NixOS manual (accessible by running ‘nixos-help’).
-{ pkgs, config, hostname, ... }:
+{
+  pkgs,
+  config,
+  hostname,
+  ...
+}:
 {
   nix = {
     settings = {
@@ -18,10 +23,10 @@
 
   # install the most recent stable linux kernel
   /*
-  TODO: change this back to 'pkgs.linuxPackages_latest' once
-  https://github.com/NixOS/nixpkgs/commit/c805021f3a95da44a1811f1235b997f57d893dc3
-  and https://github.com/NixOS/nixpkgs/pull/375838
-  trickle down to nixos-unstable
+    TODO: change this back to 'pkgs.linuxPackages_latest' once
+    https://github.com/NixOS/nixpkgs/commit/c805021f3a95da44a1811f1235b997f57d893dc3
+    and https://github.com/NixOS/nixpkgs/pull/375838
+    trickle down to nixos-unstable
   */
   boot.kernelPackages = pkgs.linuxPackages_6_12;
 
@@ -79,11 +84,11 @@
 
   # Add /etc/current-system-packages
   environment.etc."current-system-packages".text =
-  let
-    packages = builtins.map (p: "${p.name}") config.environment.systemPackages;
-    sortedUnique = builtins.sort builtins.lessThan (pkgs.lib.lists.unique packages);
-    formatted = builtins.concatStringsSep "\n" sortedUnique;
-  in
+    let
+      packages = builtins.map (p: "${p.name}") config.environment.systemPackages;
+      sortedUnique = builtins.sort builtins.lessThan (pkgs.lib.lists.unique packages);
+      formatted = builtins.concatStringsSep "\n" sortedUnique;
+    in
     formatted;
 
   # Enable CUPS to print documents.
@@ -132,17 +137,27 @@
   # programs.mtr.enable = true;
   programs.gnupg.agent = {
     enable = true;
-    enableSSHSupport = true;
+    # enableSSHSupport = true;
+    enableExtraSocket = true; # VSCode devcontainers require this
+  };
+  programs.ssh = {
+    startAgent = true;
+    extraConfig = ''
+      AddKeysToAgent yes
+      IdentityFile ~/.ssh/id_ed25519
+    '';
   };
 
   # PAM modules
   security.pam = {
-    loginLimits = [{
-      domain = "*";
-      type = "soft";
-      item = "nofile";
-      value = 8192;
-    }];
+    loginLimits = [
+      {
+        domain = "*";
+        type = "soft";
+        item = "nofile";
+        value = 8192;
+      }
+    ];
   };
 
   # List services that you want to enable: