nixos/git-daemon: only create git user if it will be used

nixos/tests/gitdaemon.nix

@@ -0,0 +1,64 @@
+import ./make-test-python.nix ({ pkgs, ... }:
+
+let
+  hashes = pkgs.writeText "hashes" ''
+    b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c  /project/bar
+  '';
+in {
+  name = "gitdaemon";
+
+  meta = with pkgs.stdenv.lib.maintainers; {
+    maintainers = [ tilpner ];
+  };
+
+  nodes = {
+    server =
+      { config, ... }: {
+        networking.firewall.allowedTCPPorts = [ config.services.gitDaemon.port ];
+
+        environment.systemPackages = [ pkgs.git ];
+
+        services.gitDaemon = {
+          enable = true;
+          basePath = "/git";
+        };
+      };
+
+    client =
+      { pkgs, ... }: {
+        environment.systemPackages = [ pkgs.git ];
+      };
+  };
+
+  testScript = ''
+    start_all()
+
+    with subtest("create project.git"):
+        server.succeed(
+            "mkdir /git",
+            "git init --bare /git/project.git",
+            "touch /git/project.git/git-daemon-export-ok",
+        )
+
+    with subtest("add file to project.git"):
+        server.succeed(
+            "git clone /git/project.git /project",
+            "echo foo > /project/bar",
+            "git config --global user.email 'you@example.com'",
+            "git config --global user.name 'Your Name'",
+            "git -C /project add bar",
+            "git -C /project commit -m 'quux'",
+            "git -C /project push",
+            "rm -r /project",
+        )
+
+    with subtest("git daemon starts"):
+        server.wait_for_unit("git-daemon.service")
+
+    with subtest("client can clone project.git"):
+        client.succeed(
+            "git clone git://server/project.git /project",
+            "sha256sum -c ${hashes}",
+        )
+  '';
+})