ci: set bash as default shell, move committing changes to a different…

… step [skip netlify]

.github/workflows/update-themes.yml

@@ -8,6 +8,10 @@ env:
 jobs:
   build:
     runs-on: ubuntu-latest
+    # Use bash shell for all steps in the workflow
+    defaults:
+      run:
+        shell: bash
     env:
       HUGO_CACHEDIR: /tmp/hugo_cache
       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -17,16 +21,22 @@ jobs:
         with:
           go-version: "^1.21.0"
       - name: Update submodules
-        shell: bash
         working-directory: ./cmd/hugothemesitebuilder
         run: |
-          git config --global user.email "bep@users.noreply.github.com"
-          git config --global user.name "bep"
           go install github.com/gohugoio/hugo@${{ env.HUGO_VERSION }}
           go run main.go build -skipSiteBuild -cleanCache
           cd build
           hugo mod get
           hugo mod tidy
+      - name: Commit & push changes
+        # Check the github.ref context to determine the current branch name. if it is 'refs/heads/main', then commit and push the changes.
+        # This allows experimenting/debugging GitHub actions without concerns about committing changes.
+        # For example, changes can be made to this workflow in a separate branch and a workflow run can be triggered manually (workflow_dispatch).
+        # For more information, see https://docs.github.com/en/actions/learn-github-actions/contexts
+        if: ${{ github.ref == 'refs/heads/main' }}
+        run: |
+          git config --global user.email "bep@users.noreply.github.com"
+          git config --global user.name "bep"
           git add .
           git commit -am "[Bot] Update themes"
           git push --force-with-lease