ci: only run check-renovaterc when the renovaterc changes

Otherwise we are just wasting CI time

.forgejo/workflows/check.yml

@@ -5,27 +5,19 @@ jobs:
     runs-on: nixos
     steps:
       - uses: "https://git.salame.cl/actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683" # v4
+      - run: nix --version
       - name: Run checks
         run: |
-          nix --version
           nix-fast-build --max-jobs 2 --no-nom --skip-cached --no-link \
             --flake ".#checks.$(nix eval --raw --impure --expr builtins.currentSystem)"
-  check-renovaterc:
-    runs-on: nixos
-    steps:
-      - uses: "https://git.salame.cl/actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683" # v4
-      - name: Validate renovaterc.json
-        run: |
-          nix --version
-          nix shell nixpkgs#renovate --command renovate-config-validator
   build-packages:
     runs-on: nixos
     needs: check
     steps:
       - uses: "https://git.salame.cl/actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683" # v4
+      - run: nix --version
       - name: Build target
         run: |
-          nix --version
           nix-fast-build --max-jobs 1 --no-nom --skip-cached --no-link \
             --flake ".#packages.$(nix eval --raw --impure --expr builtins.currentSystem)"
   build-vm:
@@ -33,9 +25,9 @@ jobs:
     needs: build-packages
     steps:
       - uses: "https://git.salame.cl/actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683" # v4
+      - run: nix --version
       - name: Build VM configuration
         run: |
-          nix --version
           nix build --print-build-logs '.#nixosConfigurations.vm.config.system.build.toplevel'
   report-size:
     runs-on: nixos

.forgejo/workflows/renovate.yml

@@ -0,0 +1,14 @@
+on:
+  push:
+    paths:
+      # only run if the renovate config changed
+      - renovate.json
+jobs:
+  check-renovaterc:
+    runs-on: nixos
+    steps:
+      - uses: https://git.salame.cl/actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - run: nix --version
+      - name: Validate renovaterc.json
+        run: |
+          nix shell nixpkgs#renovate --command renovate-config-validator