feat(third_party/cgit): Add derivation to build cgit

This is pretty much exactly the derivation from nixpkgs, with some
things removed to reduce the closure size (e.g. the various formatters
used in the default cgit version, which are replaced by cheddar in my
setup).

third_party/cgit/.skip-subtree

@@ -0,0 +1 @@
+Subtrees of this directory belong to cgit (third-party).

third_party/cgit/default.nix

@@ -0,0 +1,37 @@
+{ pkgs, ... }:
+
+let
+  inherit (pkgs.third_party) stdenv gzip bzip2 xz luajit zlib autoconf openssl pkgconfig;
+in stdenv.mkDerivation rec {
+  pname = "cgit";
+  version = "master";
+  src = ./.;
+
+  nativeBuildInputs = [ autoconf pkgconfig ];
+  buildInputs = [ openssl zlib luajit ];
+
+  postPatch = ''
+    sed -e 's|"gzip"|"${gzip}/bin/gzip"|' \
+        -e 's|"bzip2"|"${bzip2.bin}/bin/bzip2"|' \
+        -e 's|"xz"|"${xz.bin}/bin/xz"|' \
+        -i ui-snapshot.c
+  '';
+
+  # Give cgit the git source tree from the depot. Note that the
+  # versions should be kept in sync (see the Makefile for the current
+  # git version).
+  preBuild = ''
+    rm -rf git # remove submodule dir ...
+    cp -r --no-preserve=ownership,mode ${pkgs.third_party.git.src} git
+    makeFlagsArray+=(prefix="$out" CGIT_SCRIPT_PATH="$out/cgit/")
+  '';
+
+  meta = {
+    homepage = https://git.zx2c4.com/cgit/about/;
+    repositories.git = git://git.zx2c4.com/cgit;
+    description = "Web frontend for git repositories";
+    license = stdenv.lib.licenses.gpl2;
+    platforms = stdenv.lib.platforms.linux;
+    maintainers = with stdenv.lib.maintainers; [ bjornfor ];
+  };
+}

third_party/default.nix

@@ -24,6 +24,7 @@ let
       bashInteractive
       bat
       buildGoPackage
+      bzip2
       cacert
       cachix
       cargo
@@ -54,6 +55,7 @@ let
       lib
       lispPackages
       llvmPackages
+      luajit
       luatex
       makeFontsConf
       makeWrapper
@@ -91,6 +93,7 @@ let
       writeShellScriptBin
       writeText
       writeTextFile
+      xz
       zlib
       zstd;
   };