qshowdiff: Remove (Qt4)

No maintainer, no updates since introduction in 2010 except a bunch of
build/infrastructure related fixes.

Upstream's last commit is from 2018, GitHub links to
http://qshowdiff.danfis.cz which yields 404.

See #174634.

pkgs/tools/text/qshowdiff/default.nix

@@ -1,27 +0,0 @@
-{ lib, stdenv, fetchFromGitHub, qt4, perl, pkg-config }:
-
-stdenv.mkDerivation rec {
-  pname = "qshowdiff";
-  version = "1.2";
-
-  src = fetchFromGitHub {
-    owner = "danfis";
-    repo = "qshowdiff";
-    rev = "v${version}";
-    sha256 = "g3AWQ6/LSF59ztzdgNuLi+8d6fFTPiC9z0yXMdPdB5U=";
-  };
-
-  nativeBuildInputs = [ pkg-config ];
-  buildInputs = [ qt4 perl ];
-
-  configurePhase = ''
-    mkdir -p $out/{bin,man/man1}
-    makeFlags="PREFIX=$out CC=$CXX"
-  '';
-
-  meta = {
-    homepage = "http://qshowdiff.danfis.cz/";
-    description = "Colourful diff viewer";
-    license = lib.licenses.gpl3Plus;
-  };
-}

pkgs/top-level/aliases.nix

@@ -1168,6 +1168,7 @@ mapAliases ({
   qflipper = qFlipper; # Added 2022-02-11
   qmk_firmware = throw "qmk_firmware has been removed because it was broken"; # Added 2021-04-02
   qr-filetransfer = throw ''"qr-filetransfer" has been renamed to "qrcp"''; # Added 2020-12-02
+  qshowdiff = throw "'qshowdiff' (Qt4) is unmaintained and not been updated since its addition in 2010"; # Added 2022-06-14
   qt-3 = throw "qt-3 has been removed from nixpkgs, as it's unmaintained and insecure"; # Added 2021-02-15
   qt5ct = libsForQt5.qt5ct; # Added 2021-12-27
   qtcurve = libsForQt5.qtcurve; # Added 2020-11-07

pkgs/top-level/all-packages.nix

@@ -9757,8 +9757,6 @@ with pkgs;
 
   qscintilla-qt4 = callPackage ../development/libraries/qscintilla-qt4 { };
 
-  qshowdiff = callPackage ../tools/text/qshowdiff { };
-
   qrcp = callPackage ../tools/networking/qrcp { };
 
   qtikz = libsForQt5.callPackage ../applications/graphics/ktikz { };