Drv (eval) store transport

[blaggacao]

Suppose I have a hydra-like evaluator action that runs first.

This action produces all necessary .drv files for my workers.

Then I want to:

nix-store --export $(nix-store --query --requisites my.drv) \
          | $compress > $GH_CACHE

And likewise on the receiving end:

$GH_CACHE > $decompress | nix-store --import &>/dev/null

Is there a way that magic-nix-cache can provide auxiliar facilities to make this manual pushing to the GH cache easy?

---

Workaround / Solution(?):

    - uses: actions/cache/save@v3
      id: cache
      with:
        path: ${{ runner.temp }}/eval-store
        key: drv-pack-${{ runner.os }}-${{ runner.arch }}

  mkdir -p "$EVALSTORE_EXPORT"
  # nix >= 2.6.1 for the --stdin flag to avoid "too many arguments"
  nix-store --query --requisites "$drv" | nix-store --stdin --export | zstd > "$EVALSTORE_EXPORT/$(basename $drv).zst"

and then

    - uses: actions/cache/restore@v3
      id: cache
      with:
        path: ${{ runner.temp }}/eval-store
        key: drv-pack-${{ runner.os }}-${{ runner.arch }}
        fail-on-cache-miss: true

cat "$EVALSTORE_IMPORT/$(basename $actionDrv).zst" | unzstd | nix-store --import &>/dev/null