workflow: test post-build hook

.github/workflows/build-machines-and-homes.yml

@@ -39,6 +39,17 @@ jobs:
       - name: setup binary cache key
         run: echo -n "${{ secrets.NIX_CACHE_SECRET_KEY }}" | xxd -p -r > ${{ runner.temp }}/cache-priv-key.pem
 
+      - name: Sync repository
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: post-build-hook
+        run: |
+          sudo mkdir -p /etc/nix
+          sudo cp ci/upload-to-cache.sh /etc/nix/
+          sudo chmod +x /etc/nix/upload-to-cache.sh
+
       - name: Install Nix
         uses: cachix/install-nix-action@v30
         with:
@@ -51,11 +62,7 @@ jobs:
             secret-key-files = ${{ runner.temp }}/cache-priv-key.pem
             extra-substituters = https://nixcache.cy7.sh
             extra-trusted-public-keys = nixcache.cy7.sh:DN3d1dt0wnXfTH03oVmTee4KgmdNdB0NY3SuzA8Fwx8=
-
-      - name: Sync repository
-        uses: actions/checkout@v4
-        with:
-          persist-credentials: false
+            post-build-hook = /etc/nix/upload-to-cache.sh
 
       - name: build
         run: |

ci/upload-to-cache.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# https://nix.dev/guides/recipes/post-build-hook.html#implementing-the-build-hook
+set -eu
+set -f # disable globbing
+export IFS=' '
+echo "Uploading paths" $OUT_PATHS
+exec nix copy --to "s3://nixcache" $OUT_PATHS