chore(deps): bump pnpm/action-setup from 3 to 4

Bumps [pnpm/action-setup](https://github.com/pnpm/action-setup) from 3 to 4.
- [Release notes](https://github.com/pnpm/action-setup/releases)
- [Commits](https://github.com/pnpm/action-setup/compare/v3...v4)

---
updated-dependencies:
- dependency-name: pnpm/action-setup
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           ref: ${{ github.event.release.tag_name }}
 
-      - uses: pnpm/action-setup@v2
+      - uses: pnpm/action-setup@v4
       - uses: actions/setup-node@v4
         with:
           cache: pnpm

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - uses: pnpm/action-setup@v2
+      - uses: pnpm/action-setup@v4
       - uses: actions/setup-node@v4
         with:
           cache: pnpm
@@ -28,7 +28,7 @@ jobs:
         run: pnpm install && pnpm build
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v7
+        uses: DeterminateSystems/nix-installer-action@v9
 
       - name: Setup Attic Cache
         uses: ./

src/index.ts

@@ -1,12 +1,16 @@
-import { install } from "./stages/install";
+import { install, isInstalled } from "./stages/install";
 import { configure } from "./stages/configure";
 import { push } from "./stages/push";
-import { getState, saveState } from "@actions/core";
+import { getState, saveState, info } from "@actions/core";
 
 const isPost = !!getState("isPost");
 
 const main = async () => {
+	if (await isInstalled()) {
+		info("Skipping attic installation because it is already installed");
+	} else {
 		await install();
+	}
 	await configure();
 };
 

src/stages/install.ts

@@ -33,3 +33,8 @@ export const install = async () => {
 
 	core.endGroup();
 };
+
+export const isInstalled = async () => {
+	let return_code = await exec("attic", ["-V"]);
+	return return_code === 0;
+};