attempt to fix Github Actions caching

Author: peterbecich

.github/workflows/nix-shell.yml

@@ -21,9 +21,9 @@ jobs:
     - name: Cache nix env take N+1
       uses: actions/[email protected]
       with:
-        path: |
+        path: /nix/store
           # See https://github.com/actions/cache/pull/726
-          /nix/store/**
+          # /nix/store/**
           # Missing something?
           # /nix/var/nix/*/*
           # /nix/var/nix/db/*
@@ -33,7 +33,7 @@ jobs:
           # !/nix/var/nix/gc.lock
           # !/nix/var/nix/db/big-lock
           # !/nix/var/nix/db/reserved
-        key: ${{ runner.os }}-nix-store-${{ hashFiles('**') }}
+        key: ${{ runner.os }}-nix-store-${{ hashFiles('/nix/store/**') }}
         restore-keys: ${{ runner.os }}-nix-store-
 
     - uses: cachix/install-nix-action@v16