rip2: Add shell completions

pkgs/by-name/ri/rip2/package.nix

@@ -3,6 +3,8 @@
   rustPlatform,
   fetchFromGitHub,
   versionCheckHook,
+  installShellFiles,
+  stdenv,
 }:
 
 rustPlatform.buildRustPackage rec {
@@ -18,6 +20,8 @@ rustPlatform.buildRustPackage rec {
 
   cargoHash = "sha256-l6rbeiyIsr1csBcp+428TpQYSs9RvfJutGoL/wtSGR8=";
 
+  nativeBuildInputs = [ installShellFiles ];
+
   # TODO: Unsure why this test fails, but not a major issue so
   #       skipping for now.
   checkFlags = [ "--skip=test_filetypes::file_type_3___fifo__" ];
@@ -25,6 +29,12 @@ rustPlatform.buildRustPackage rec {
   doInstallCheck = true;
   nativeInstallCheckInputs = [ versionCheckHook ];
   versionCheckProgram = "${placeholder "out"}/bin/rip";
+  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+    installShellCompletion --cmd rip \
+      --bash <($out/bin/rip completions bash) \
+      --fish <($out/bin/rip completions fish) \
+      --zsh <($out/bin/rip completions zsh)
+  '';
 
   meta = {
     description = "Safe and ergonomic alternative to rm";