add git settings on mac to enable ssh commit signing via 1P

machines/darwin/pepacton/default.nix

@@ -1,5 +1,5 @@
 # Reference: https://daiderd.com/nix-darwin/manual/index.html
-{pkgs, config, ...}: {
+{pkgs, ...}: {
   users.users.henrikvt = {
     home = "/Users/henrikvt";
     packages = with pkgs; [
@@ -15,6 +15,13 @@
     rebuild = "darwin-rebuild switch --flake /Users/henrikvt/Desktop/Code/projects/nixmachines#pepacton";
   };
 
+  home-manager.users.henrikvt.programs.git.extraConfig = {
+    user.signingkey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICM+1ip8IBO+sK8J7cOwEtA/ba+tTtPHUGYC/KW6mppU";
+    gpg.format = "ssh";
+    gpg.ssh.program = "/Applications/1Password.app/Contents/MacOS/op-ssh-sign";
+    commit.gpgsign = true;
+  };
+
   networking.hostName = "pepacton";
 
   nixpkgs.hostPlatform = "aarch64-darwin";