use extra-conf instead of independent nix.conf

Signed-off-by: Thing-han, Lim <[email protected]>

.github/actions/setup-nix/action.yml

@@ -14,26 +14,27 @@ inputs:
 runs:
   using: composite
   steps:
-    - name: Check nix
-      id: check-nix
+    - name: Pre-check nix
+      id: pre-check-nix
       continue-on-error: true
       shell: bash
       run: |
         nix --version
-        nix show-config | grep -E "^trusted-users = .*$USER"
-        nix show-config | grep -E "^experimental-features = .*flakes"
-        nix show-config | grep -E "^experimental-features = .*nix-command"
+        nix config show | grep -E "^trusted-users = .*$USER"
+        nix config show | grep -E "^experimental-features = .*flakes"
+        nix config show | grep -E "^experimental-features = .*nix-command"
 
     - name: Install nix
-      if: steps.check-nix.outcome != 'success'
+      if: steps.pre-check-nix.outcome != 'success'
       shell: bash
       run: |
-        curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install --no-confirm
-        echo "trusted-users = root ${USER:-}" >> nix.conf
-        echo "experimental-features = nix-command flakes" >> nix.conf
-        sudo mkdir -p /etc/nix
-        sudo chmod 0755 /etc/nix
-        sudo cp nix.conf /etc/nix/nix.conf
+        curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install --no-confirm \
+        --extra-conf "trusted-users = root ${USER:-}" \
+        --extra-conf "experimental-features = nix-command flakes" \
+    - name: Post-check nix
+      shell: bash
+      run: |
+        nix config check
     - uses: DeterminateSystems/magic-nix-cache-action@v8
     - name: Prepare nix dev shell
       shell: nix develop --quiet .#${{ inputs.devShell }} -c bash -e {0}