chore: re-add nix stuff from @waalge

Co-authored-by: waalge

.gitignore

@@ -1,3 +1,4 @@
+/.direnv
 /target
 .idea
 _site/

crates/aiken/src/main.rs

@@ -63,9 +63,12 @@ fn main() -> miette::Result<()> {
 }
 
 fn version() -> String {
+    use std::env;
+    let nix_git_rev = env::var("GIT_REVISION").unwrap_or("unknown".to_string());
+
     format!(
         "v{} {}",
         built_info::PKG_VERSION,
-        built_info::GIT_COMMIT_HASH_SHORT.unwrap_or("unknown")
+        built_info::GIT_COMMIT_HASH_SHORT.unwrap_or(&nix_git_rev)
     )
 }

flake.nix

@@ -54,10 +54,18 @@
             package = packages.aiken;
           }
         ];
-      in rec {
+
+        gitRev = if (builtins.hasAttr "rev" self)
+            then self.rev
+            else "dirty";
+      in {
         inherit packages;
         devShell = rustPkgs.workspaceShell {
           packages = [deno];
+          shellHook =
+          ''
+            export GIT_REVISION=${gitRev}
+          '';
         };
         devShells = {
           aiken = pkgs.devshell.mkShell {