feat: initial macos setup

justfile

@@ -1,14 +1,20 @@
 set positional-arguments
 
-host := `hostname`
+# Flake host key. On macOS the LocalHostName is what matches the flake key
+# (after the first rebuild); on Linux it's the plain hostname.
+# Override:  just host=myname rebuild
+host := if os() == "macos" { `scutil --get LocalHostName` } else { `hostname` }
+
+# Pick the rebuild tool for the current OS.
+rebuild-cmd := if os() == "macos" { "darwin-rebuild" } else { "nixos-rebuild" }
 
 # Default: list available recipes.
 default:
     @just --list
 
-# Rebuild the system and switch immediately
+# Rebuild the system and switch immediately. Works on NixOS and macOS.
 rebuild:
-    sudo nixos-rebuild switch --flake .#{{host}}
+    sudo {{rebuild-cmd}} switch --flake .#{{host}}
 
 # Update flake.lock
 update:
@@ -18,7 +24,7 @@ update:
 clean:
     sudo nix-collect-garbage --delete-older-than 7d
     sudo nix-store --optimise
-    sudo nixos-rebuild boot --flake .#{{host}}
+    sudo {{ if os() == "macos" { "darwin-rebuild switch" } else { "nixos-rebuild boot" } }} --flake .#{{host}}
 
 # Generate Ed25519 SSH keys for each named service (default: github gradescope).
 # Override:  just gen-keys gitlab bitbucket