make nixos.nix reusable rather than opinionated

Signed-off-by: Kiara Grouwstra <kiara@procolix.eu>

deployment/check/data-model-ssh/nixosTest.nix

@@ -4,10 +4,9 @@
   ...
 }:
 let
-  inherit (import ./constants.nix) pathToRoot pathFromRoot;
   inherit (pkgs) system;
   deployment-config = {
-    inherit pathToRoot pathFromRoot;
+    inherit (import ./constants.nix) pathToRoot;
     nodeName = "ssh";
     targetSystem = system;
     sshOpts = [ ];

deployment/check/data-model-tf/nixosTest.nix

@@ -4,10 +4,9 @@
   ...
 }:
 let
-  inherit (import ./constants.nix) pathToRoot pathFromRoot;
   inherit (pkgs) system;
   deployment-config = {
-    inherit pathToRoot pathFromRoot;
+    inherit (import ./constants.nix) pathToRoot;
     nodeName = "target";
     targetSystem = system;
     sshOpts = [ ];

deployment/nixos.nix

@@ -11,15 +11,9 @@ let
     };
     modules = [ configuration ];
   };
-  toplevel =
-    {
-      inherit (eval) pkgs config options;
-      system = eval.config.system.build.toplevel;
-      inherit (eval.config.system.build) vm vmWithBootLoader;
-    }
-    .config.system.build.toplevel;
 in
 {
-  drv_path = toplevel.drvPath;
-  out_path = toplevel;
+  inherit (eval) pkgs config options;
+  system = eval.config.system.build.toplevel;
+  inherit (eval.config.system.build) vm vmWithBootLoader;
 }

deployment/run/ssh-single-host/run.sh

@@ -24,13 +24,13 @@ command=(nix-instantiate --show-trace "${nixos_conf}")
 
 # INSTANTIATE
 # instantiate the config in /nix/store
-"${command[@]}" -A out_path
+"${command[@]}" -A config.system.build.toplevel
 
-# get the realized derivation to deploy
-"${command[@]}" --show-trace --eval --strict --json
+# get the realized derivation so we can deploy it
+"${command[@]}" -A config.system.build.toplevel --eval --strict --json
 
 # FIXME explore import/readFile as ways to instantiate the derivation, potentially allowing to realize the store path up-front from Nix?
-outPath=$(nix-store --realize "$("${command[@]}" --show-trace --eval --strict --json | jq -r '.drv_path')")
+outPath=$(nix-store --realize "$("${command[@]}" -A config.system.build.toplevel.drvPath --eval --strict --json | jq -r '.')")
 # deploy the config by nix-copy-closure
 NIX_SSHOPTS="${sshOpts[*]}" nix-copy-closure --to "$destination" "$outPath" --gzip --use-substitutes
 # switch the remote host to the config