ci: don't build dependabot prs

* this also only build PRs, pushes to main and tags.

* this also only build PRs, pushes to main and tags.

.github/workflows/CI.yml

@@ -4,9 +4,16 @@ on:
   push:
     paths-ignore:
       - "**.md"
+    branches:
+      - 'main'
+  # this is needed when pushing tags manually, apparantly.
+  # https://github.com/actions/runner/issues/1007
+  create:
   pull_request:
     paths-ignore:
       - "**.md"
+    branches-ignore:
+      - 'dependabot/*'
 jobs:
   CI:
     runs-on: ubuntu-latest
@@ -29,7 +36,6 @@ jobs:
       with:
         install_url: https://releases.nixos.org/nix/nix-2.18.4/install
     - name: "Set Up Binary Cache"
-      if: github.event_name != 'pull_request'
       uses: cachix/cachix-action@v15
       with:
         name: t2linux
@@ -49,7 +55,7 @@ jobs:
           rm result
         done
     - name: Release
-      uses: softprops/action-gh-release@v1
-      if: startsWith(github.ref, 'refs/tags/v') && contains(github.ref, '.')
+      uses: softprops/action-gh-release@v2
+      if: startsWith(github.ref, 'refs/tags/v')
       with:
         files: "nixos-*.iso*"