circleci-cli: Add shell completions

pkgs/development/tools/misc/circleci-cli/default.nix

@@ -1,4 +1,4 @@
-{ lib, fetchFromGitHub, buildGoModule }:
+{ lib, fetchFromGitHub, buildGoModule, installShellFiles }:
 
 buildGoModule rec {
   pname = "circleci-cli";
@@ -13,12 +13,18 @@ buildGoModule rec {
 
   vendorSha256 = "sha256-jrAd1G/NCjXfaJmzOhMjMZfJoGHsQ1bi3HudBM0e8rE=";
 
+  nativeBuildInputs = [ installShellFiles ];
+
   doCheck = false;
 
   ldflags = [ "-s" "-w" "-X github.com/CircleCI-Public/circleci-cli/version.Version=${version}" "-X github.com/CircleCI-Public/circleci-cli/version.Commit=${src.rev}" "-X github.com/CircleCI-Public/circleci-cli/version.packageManager=nix" ];
 
   postInstall = ''
     mv $out/bin/circleci-cli $out/bin/circleci
+
+    installShellCompletion --cmd circleci \
+      --bash <($out/bin/circleci completion bash --skip-update-check) \
+      --zsh <($out/bin/circleci completion zsh --skip-update-check)
   '';
 
   meta = with lib; {