incus: add statically compiled client

The incus client can be used from non-Linux systems, and as a
standalone binary. Therefore, compile the client separately, and give
it a separate passthru so users can install `incus.client`.

pkgs/by-name/in/incus/client.nix

@@ -0,0 +1,53 @@
+{
+  lts ? false,
+
+  lib,
+  buildGoModule,
+  fetchFromGitHub,
+  installShellFiles,
+}:
+let
+  releaseFile = if lts then ./lts.nix else ./latest.nix;
+  inherit (import releaseFile) version hash vendorHash;
+in
+
+buildGoModule rec {
+  pname = "incus-client";
+
+  inherit vendorHash version;
+
+  src = fetchFromGitHub {
+    owner = "lxc";
+    repo = "incus";
+    rev = "refs/tags/v${version}";
+    inherit hash;
+  };
+
+  CGO_ENABLED = 0;
+
+  nativeBuildInputs = [ installShellFiles ];
+
+  subPackages = [ "cmd/incus" ];
+
+  postInstall = ''
+    # use custom bash completion as it has extra logic for e.g. instance names
+    installShellCompletion --bash --name incus ./scripts/bash/incus
+
+    installShellCompletion --cmd incus \
+      --fish <($out/bin/incus completion fish) \
+      --zsh <($out/bin/incus completion zsh)
+  '';
+
+  # don't run the full incus test suite
+  doCheck = false;
+
+  meta = {
+    description = "Powerful system container and virtual machine manager";
+    homepage = "https://linuxcontainers.org/incus";
+    changelog = "https://github.com/lxc/incus/releases/tag/v${version}";
+    license = lib.licenses.asl20;
+    maintainers = lib.teams.lxc.members;
+    platforms = lib.platforms.unix;
+    mainProgram = "incus";
+  };
+}

pkgs/by-name/in/incus/package.nix

@@ -41,6 +41,7 @@
 }:
 let
   unwrapped = callPackage ./unwrapped.nix { inherit lts; };
+  client = callPackage ./client.nix { inherit lts; };
 
   binPath = lib.makeBinPath [
     acl
@@ -164,6 +165,8 @@ symlinkJoin {
   passthru = {
     inherit (unwrapped) tests;
 
+    client = client;
+
     unwrapped = unwrapped;
   };