feat: automatically configure Nix to use cache (#8)

action.yml

@@ -19,6 +19,9 @@ inputs:
   token:
     description: "Attic authorization token"
     required: false
+  skip-use:
+    description: "Set to true to skip using attic cache as a substituter"
+    required: false
 
 runs:
   using: "node16"

src/stages/configure.ts

@@ -9,10 +9,18 @@ export const configure = async () => {
 		const endpoint = core.getInput("endpoint");
 		const cache = core.getInput("cache");
 		const token = core.getInput("token");
+		const skipUse = core.getInput("skip-use");
 
 		core.info("Logging in to attic cache");
 		await exec("attic", ["login", "--set-default", cache, endpoint, token]);
 
+		if (skipUse === "true") {
+			core.info('Not adding attic cache to substituters as skip-use is set to true');
+		} else {
+			core.info("Adding attic cache to substituters");
+			await exec.exec('attic', ['use', cache]);
+		}
+
 		core.info("Collecting store paths before build");
 		await saveStorePaths();
 	} catch (e) {