chore(devshell): Use deploy-rs from nixpkgs for binary caching

flake.nix

@@ -63,7 +63,6 @@
       self,
       nixpkgs,
       sops-nix,
-      deploy-rs,
       ...
     }@inputs:
     let
@@ -78,6 +77,25 @@
           ./configuration/hardware-specific/vm.nix
         ];
       };
+
+      # deploy-rs unfortunately uses an `import nixpkgs`, and its
+      # library functions depend on an instantiated nixpkgs, so we
+      # can't get around multi-nixpkgs-eval.
+      inherit
+        (import nixpkgs {
+          inherit system;
+          overlays = [
+            inputs.deploy-rs.overlays.default
+            (_: prev: {
+              deploy-rs = {
+                inherit (nixpkgs.legacyPackages.${system}) deploy-rs;
+                inherit (prev.deploy-rs) lib;
+              };
+            })
+          ];
+        })
+        deploy-rs
+        ;
     in
     {
       ##################
@@ -105,7 +123,7 @@
 
           profiles.system = {
             user = "root";
-            path = deploy-rs.lib.${system}.activate.nixos self.nixosConfigurations.hetzner-1;
+            path = deploy-rs.lib.activate.nixos self.nixosConfigurations.hetzner-1;
           };
 
           sshUser = "tlater";
@@ -159,7 +177,7 @@
 
           packages = nixpkgs.lib.attrValues {
             inherit (sops-nix.packages.${system}) sops-import-keys-hook sops-init-gpg-key;
-            inherit (deploy-rs.packages.${system}) default;
+            inherit (deploy-rs) deploy-rs;
           };
         };