saml2aws: install shell completion (#339219)

pkgs/tools/security/saml2aws/default.nix

@@ -1,4 +1,11 @@
-{ lib, stdenv, buildGoModule, fetchFromGitHub, AppKit }:
+{
+  lib,
+  stdenv,
+  buildGoModule,
+  fetchFromGitHub,
+  installShellFiles,
+  AppKit,
+}:
 
 buildGoModule rec {
   pname = "saml2aws";
@@ -13,19 +20,29 @@ buildGoModule rec {
 
   vendorHash = "sha256-gtl8T8wXnpLgDZc6qSgFKpA+XbcLNHf20ieBkyNdE+s=";
 
+  nativeBuildInputs = [ installShellFiles ];
   buildInputs = lib.optionals stdenv.isDarwin [ AppKit ];
 
-  subPackages = [ "." "cmd/saml2aws" ];
+  subPackages = [
+    "."
+    "cmd/saml2aws"
+  ];
 
   ldflags = [
     "-X main.Version=${version}"
   ];
 
+  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+    installShellCompletion --cmd saml2aws \
+      --bash <($out/bin/saml2aws --completion-script-bash) \
+      --zsh <($out/bin/saml2aws --completion-script-zsh)
+  '';
+
   meta = with lib; {
     description = "CLI tool which enables you to login and retrieve AWS temporary credentials using a SAML IDP";
     mainProgram = "saml2aws";
-    homepage    = "https://github.com/Versent/saml2aws";
-    license     = licenses.mit;
+    homepage = "https://github.com/Versent/saml2aws";
+    license = licenses.mit;
     maintainers = [ lib.maintainers.pmyjavec ];
   };
 }