nixos/tailscale: add package as an option

This simplifies testing changes to the tailscale service on a local
machine. You can use this as such:

```nix
let
  tailscale_patched = magic {};
in {
  services.tailscale = {
    enable = true;
    package = tailscale_patched;
  };
};
```

Signed-off-by: Christine Dodrill <me@christine.website>

1 files changed, 9 insertions, 2 deletions

diff --git a/nixos/modules/services/networking/tailscale.nix b/nixos/modules/services/networking/tailscale.nix
index d6684d69e61..1a1474595be 100644
--- a/nixos/modules/services/networking/tailscale.nix
+++ b/nixos/modules/services/networking/tailscale.nix
@@ -14,11 +14,18 @@ in {
       default = 41641;
       description = "The port to listen on for tunnel traffic (0=autoselect).";
     };
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.tailscale;
+      defaultText = "pkgs.tailscale";
+      description = "The package to use for tailscale";
+    };
   };
 
   config = mkIf cfg.enable {
-    environment.systemPackages = [ pkgs.tailscale ]; # for the CLI
-    systemd.packages = [ pkgs.tailscale ];
+    environment.systemPackages = [ cfg.package ]; # for the CLI
+    systemd.packages = [ cfg.package ];
     systemd.services.tailscaled = {
       wantedBy = [ "multi-user.target" ];
       serviceConfig.Environment = "PORT=${toString cfg.port}";