Cache nix

.forgejo/install-emacs/action.yml

@@ -7,7 +7,21 @@ inputs:
 runs:
   using: 'composite'
   steps:
+    - name: Restore cached version
+      id: cache-restore
+      uses: https://code.forgejo.org/actions/cache/restore@v4
+      with:
+        path: |
+          /nix/store
+        key: ${{ inputs.version }}-${{ hashFiles('flake.lock') }}
     - run: ${{ github.action_path }}/install.sh
       shell: bash
       env:
         INPUT_VERSION: ${{ inputs.version }}
+    - name: Cache version
+      id: cache-put
+      uses: https://code.forgejo.org/actions/cache/save@v4
+      with:
+        path: |
+          /nix/store
+        key: ${{ inputs.version }}-${{ hashFiles('flake.lock') }}

.forgejo/install-emacs/install-nix.sh

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+# Sudo is required by this installer
+apt-get update -qq
+apt-get install -y sudo
+
 if nix_path="$(type -p nix)" ; then
   echo "Aborting: Nix is already installed at ${nix_path}"
   exit
@@ -79,8 +83,6 @@ else
   # "fix" the following error when running nix*
   # error: the group 'nixbld' specified in 'build-users-group' does not exist
   add_config "build-users-group ="
-  apt-get update -qq
-  apt-get install -y sudo
   sudo mkdir -p /etc/nix
   sudo chmod 0755 /etc/nix
   sudo cp "$workdir/nix.conf" /etc/nix/nix.conf