korrect: Add shell completions

Author: dwt

pkgs/by-name/ko/korrect/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   fetchCrate,
   rustPlatform,
+  installShellFiles,
   nix-update-script,
 }:
 
@@ -19,6 +20,15 @@ rustPlatform.buildRustPackage (finalAttrs: {
 
   passthru.updateScript = nix-update-script { };
 
+  nativeBuildInputs = [ installShellFiles ];
+
+  postInstall = ''
+    installShellCompletion --cmd ${finalAttrs.pname} \
+      --bash <($out/bin/${finalAttrs.pname} completions bash) \
+      --fish <($out/bin/${finalAttrs.pname} completions fish) \
+      --zsh <($out/bin/${finalAttrs.pname} completions zsh)
+  '';
+
   meta = {
     description = "Kubectl version managing shim that invokes the correct kubectl version";
     homepage = "https://gitlab.com/cromulentbanana/korrect";