chore: extract version from main.go in flake.nix

Use builtins.match to parse version from cmd/homelab-deploy/main.go
so only one location needs updating when bumping versions.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -113,9 +113,7 @@ Follow semantic versioning:
 - **Minor** (0.x.0): Non-breaking changes adding features
 - **Major** (x.0.0): Breaking changes
 
-Update the version in **both** locations:
+Update `const version` in `cmd/homelab-deploy/main.go`. The Nix build extracts the version from there automatically.
-1. `const version` in `cmd/homelab-deploy/main.go`
-2. `version` field in `flake.nix`
 
 **When to bump**: If any Go code has changed, bump the version before committing. Do this automatically when asked to commit. On feature branches, only bump once per branch (check if version has already been bumped compared to master).
 

flake.nix

@@ -15,11 +15,16 @@
       packages = forAllSystems (system:
         let
           pkgs = pkgsFor system;
+          # Extract version from main.go
+          version = builtins.head (
+            builtins.match ''.*const version = "([^"]+)".*''
+              (builtins.readFile ./cmd/homelab-deploy/main.go)
+          );
         in
         {
           homelab-deploy = pkgs.buildGoModule {
             pname = "homelab-deploy";
-            version = "0.1.0";
+            inherit version;
             src = ./.;
             vendorHash = "sha256-JXa+obN62zrrwXlplqojY7dvEunUqDdSTee6N8c5JTg=";
             subPackages = [ "cmd/homelab-deploy" ];