Use deduplicating nix for nix copy operations

.github/workflows/build.yml

@@ -1,8 +1,5 @@
 name: build
 on:
-  push:
-    branches:
-      - main
   pull_request:
     branches:
       - main
@@ -68,8 +65,11 @@ jobs:
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
             trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= nixcache:8KKuGz95Pk4UJ5W/Ni+pN+v+LDTkMMFV4yrGmAYgkDg= hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=
             experimental-features = nix-command flakes ca-derivations
-            post-build-hook = ${{ github.workspace }}/scripts/post-build-hook
             substituters = https://cache.chir.rs/
+      - name: Download patched nix
+        run: nix build github:DarkKirb/nix-packages#nix-s3-dedup
+      - name: Setup post-build-hook
+        run: echo "post-build-hook = ${{ github.workspace }}/scripts/post-build-hook" | sudo tee -a /etc/nix/nix.conf
       - name: Set up secrets
         run: |
           echo "$NIX_CACHE_KEY" > ~/cache.key

scripts/post-build-hook

@@ -2,4 +2,4 @@
 set -euf
 export IFS=' '
 /nix/var/nix/profiles/default/bin/nix store sign --key-file /home/runner/cache.key $DRV_PATH
-/nix/var/nix/profiles/default/bin/nix copy --to 's3://cache-chir-rs?scheme=https&endpoint=s3.us-west-000.backblazeb2.com&secret-key=/home/runner/cache.key&multipart-upload=true&compression=zstd&compression-level=15' $DRV_PATH
+/nix/var/nix/profiles/default/bin/nix run 'github:DarkKirb/nix-packages#nix-s3-dedup' -- copy --to 's3://cache-chir-rs?scheme=https&endpoint=s3.us-west-000.backblazeb2.com&secret-key=/home/runner/cache.key&multipart-upload=true&compression=zstd&compression-level=15' $DRV_PATH