terraform-docs: install shell completions (#347637)

pkgs/by-name/te/terraform-docs/package.nix

@@ -1,7 +1,9 @@
 {
+  stdenv,
   lib,
   buildGoModule,
   fetchFromGitHub,
+  installShellFiles,
 }:
 buildGoModule rec {
   pname = "terraform-docs";
@@ -16,6 +18,17 @@ buildGoModule rec {
 
   vendorHash = "sha256-aweKTHQBYYqSp8CymwhnVv1WNQ7cZ1/bJNz7DSo7PKc=";
 
+  excludedPackages = [ "scripts" ];
+
+  nativeBuildInputs = [ installShellFiles ];
+
+  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+    $out/bin/terraform-docs completion bash >terraform-docs.bash
+    $out/bin/terraform-docs completion fish >terraform-docs.fish
+    $out/bin/terraform-docs completion zsh >terraform-docs.zsh
+    installShellCompletion terraform-docs.{bash,fish,zsh}
+  '';
+
   meta = with lib; {
     description = "Utility to generate documentation from Terraform modules in various output formats";
     mainProgram = "terraform-docs";