Add forge minecraft service

pkgs/default.nix

@@ -0,0 +1,6 @@
+{ pkgs, ... }:
+
+{
+  # Forge
+  forge-server = pkgs.callPackage ./minecraft/forge-server.nix { };
+}

pkgs/minecraft/forge-server.nix

@@ -0,0 +1,64 @@
+{ lib, stdenv, fetchurl, jre_headless, runtimeShell }:
+
+let
+  name = "forge-server";
+  version = "1.16.5-36.1.1";
+  mirror = "https://files.minecraftforge.net/maven/net/minecraftforge/forge";
+  src = fetchurl {
+    url = "${mirror}/${version}/forge-${version}-installer.jar";
+    # Forge doesn't seem to like newer shas
+    sha1 = "78e5bd0b19f05136bb25bf3c5be9b64a1d0e850e";
+  };
+
+  unpackCmd = "mkdir -p src; cp $curSrc src/forge-${version}-installer.jar";
+
+  # Somewhat evil pre-install step to run through the network
+  # dependency resolution forge needs. This is also common for gradle
+  # projects, so I think this is ok-ish here, though ideally I'd
+  # identify all the dependencies and package them as well.
+  deps = stdenv.mkDerivation {
+    name = "${name}-deps";
+    inherit src unpackCmd;
+
+    nativeBuildInputs = [ jre_headless ];
+    buildPhase = ''
+      java -jar forge-${version}-installer.jar --installServer installation
+    '';
+    installPhase = ''
+      mkdir -p $out
+      cp -r installation/forge-${version}.jar installation/libraries $out
+    '';
+
+    outputHashAlgo = "sha256";
+    outputHashMode = "recursive";
+    outputHash = "lV4UxmSdv/I+HwvnT8CLcHpSKyDvKnldA5/Lw1GsJ/M=";
+  };
+
+in stdenv.mkDerivation rec {
+  inherit name version src unpackCmd;
+
+  installPhase = ''
+    mkdir -p $out/{bin,lib/forge}
+    cp -rv ${deps}/* $out/lib/forge/
+
+    cat > $out/bin/forge-server << EOF
+    #!${runtimeShell}
+    set -eu
+
+    exec ${jre_headless}/bin/java \$@ -jar $out'/lib/forge/forge-${version}.jar' nogui
+    EOF
+
+    chmod +x $out/bin/forge-server
+  '';
+
+  phases = "installPhase";
+
+  meta = with lib; {
+    description = "Forge Minecraft Server";
+    homepage = "https://files.minecraftforge.net/";
+    # Forge itself is open source, but this package pulls in
+    # minecraft.
+    license = licenses.unfreeRedistributable;
+    platforms = platforms.unix;
+  };
+}