A directory-category for terminal emulators

This is a mostly cosmetical commit, in the sense it doesn't change the contents
of any package, but reorganizes the overall Nixpkgs expressions.

Terminal emulators are an ubiquitous tool for any Unix user; even the beginners
are routinely familiarized to it. And, manifestly, there are many
implementations of terminal emulators out there, from those traditionally made
in C and C++ to those written in Haskell and Go.

Terminal emulators deserve more highlight. This commit does that by creating a
category for them.

pkgs/applications/terminal-emulators/tilix/default.nix

@@ -0,0 +1,74 @@
+{ stdenv
+, fetchFromGitHub
+, fetchpatch
+, meson
+, ninja
+, python3
+, pkgconfig
+, dmd
+, dconf
+, dbus
+, gsettings-desktop-schemas
+, desktop-file-utils
+, gettext
+, gtkd
+, libsecret
+, glib
+, wrapGAppsHook
+, libunwind
+}:
+
+stdenv.mkDerivation {
+  pname = "tilix";
+  version = "unstable-2019-10-02";
+
+  src = fetchFromGitHub {
+    owner = "gnunn1";
+    repo = "tilix";
+    rev = "ffcd31e3c0e1a560ce89468152d8726065e8fb1f";
+    sha256 = "1bzv7xiqhyblz1rw8ln4zpspmml49vnshn1zsv9di5q7kfgpqrgq";
+  };
+
+  # Default upstream else LDC fails to link
+  mesonBuildType = [
+    "debugoptimized"
+  ];
+
+  nativeBuildInputs = [
+    desktop-file-utils
+    dmd
+    meson
+    ninja
+    pkgconfig
+    python3
+    wrapGAppsHook
+  ];
+
+  buildInputs = [
+    dbus
+    gettext
+    dconf
+    gsettings-desktop-schemas
+    gtkd
+    libsecret
+    libunwind
+  ];
+
+  postPatch = ''
+    chmod +x meson_post_install.py
+    patchShebangs meson_post_install.py
+  '';
+
+  preFixup = ''
+    substituteInPlace $out/share/applications/com.gexperts.Tilix.desktop \
+      --replace "Exec=tilix" "Exec=$out/bin/tilix"
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Tiling terminal emulator following the Gnome Human Interface Guidelines";
+    homepage = "https://gnunn1.github.io/tilix-web";
+    license = licenses.mpl20;
+    maintainers = with maintainers; [ midchildan worldofpeace ];
+    platforms = platforms.linux;
+  };
+}