nix-top: init at 0.3.0

This was removed in 329081dc4b, but
since I find this package useful, I'll make an attempt to maintain it.
Fortunately someone had forked the repo before it was deleted.

The derivation has been modified slightly to reflect PR feedback.

pkgs/by-name/ni/nix-top/package.nix

@@ -0,0 +1,62 @@
+{
+  binutils-unwrapped, # strings
+  coreutils,
+  getent, # /etc/passwd
+  fetchFromGitHub,
+  findutils,
+  lib,
+  makeWrapper,
+  ncurses, # tput
+  ruby,
+  stdenv,
+}:
+
+# No gems used, so mkDerivation is fine.
+let
+  additionalPath = lib.makeBinPath [
+    getent
+    ncurses
+    binutils-unwrapped
+    coreutils
+    findutils
+  ];
+in
+stdenv.mkDerivation rec {
+  pname = "nix-top";
+  version = "0.3.0";
+
+  src = fetchFromGitHub {
+    owner = "jerith666";
+    repo = "nix-top";
+    rev = "v${version}";
+    hash = "sha256-w/TKzbZmMt4CX2KnLwPvR1ydp5NNlp9nNx78jJvhp54=";
+  };
+
+  nativeBuildInputs = [ makeWrapper ];
+
+  buildInputs = [ ruby ];
+
+  installPhase =
+    ''
+      runHook preInstall
+      mkdir -p $out/libexec/nix-top
+      install -D -m755 ./nix-top $out/bin/nix-top
+      wrapProgram $out/bin/nix-top \
+        --prefix PATH : "$out/libexec/nix-top:${additionalPath}"
+    ''
+    + lib.optionalString stdenv.isDarwin ''
+      ln -s /bin/stty $out/libexec/nix-top
+    ''
+    + ''
+      runHook postInstall
+    '';
+
+  meta = {
+    description = "Tracks what nix is building";
+    homepage = "https://github.com/jerith666/nix-top";
+    license = lib.licenses.mit;
+    maintainers = [ lib.maintainers.jerith666 ];
+    platforms = lib.platforms.unix;
+    mainProgram = "nix-top";
+  };
+}

pkgs/top-level/aliases.nix

@@ -950,7 +950,6 @@ mapAliases ({
   );
   nix-review = throw "'nix-review' has been renamed to/replaced by 'nixpkgs-review'"; # Converted to throw 2023-09-10
   nix-template-rpm = throw "'nix-template-rpm' has been removed as it is broken and unmaintained"; # Added 2023-11-20
-  nix-top = throw "The nix-top package was dropped since it was unmaintained."; # Added 2024-06-21
   nix-universal-prefetch = throw "The nix-universal-prefetch package was dropped since it was unmaintained."; # Added 2024-06-21
   nixFlakes = nixVersions.stable; # Added 2021-05-21
   nixStable = nixVersions.stable; # Added 2022-01-24