jx: install completions

pkgs/applications/networking/cluster/jx/default.nix

@@ -1,4 +1,4 @@
-{ buildGoModule, fetchFromGitHub, lib }:
+{ buildGoModule, fetchFromGitHub, lib, installShellFiles }:
 
 buildGoModule rec {
   pname = "jx";
@@ -15,12 +15,21 @@ buildGoModule rec {
 
   subPackages = [ "cmd/jx" ];
 
+  nativeBuildInputs = [ installShellFiles ];
+
   buildFlagsArray = ''
     -ldflags=
     -X github.com/jenkins-x/jx/pkg/version.Version=${version}
     -X github.com/jenkins-x/jx/pkg/version.Revision=${version}
   '';
 
+  postInstall = ''
+    for shell in bash zsh; do
+      $out/bin/jx completion $shell > jx.$shell
+      installShellCompletion jx.$shell
+    done
+  '';
+
   meta = with lib; {
     description = "JX is a command line tool for installing and using Jenkins X.";
     homepage = "https://jenkins-x.io";