infra: ensure template alignment across branches

This commit implements a vital check to ensure consistent template alignment between the master
branch and other branches. It enforces that template files on the master branch remain the
definitive source of truth.
This decreases maintainance effort by having less files.

This check will get only activated on PRs that touch template files,
in order to not block unrelated work on the branches.

.github/workflows/template-check.yml

@@ -59,3 +59,45 @@ jobs:
               exit 1
             fi
           done
+
+  infra-template-master-match-check:
+    runs-on: ubuntu-20.04
+    name: Compare templates files with master branch
+    if: github.event.pull_request.base.ref != 'master'
+
+    steps:
+      - name: Clone Anaconda repository
+        uses: actions/checkout@v3
+        with:
+          # TODO: Are we able to remove ref, fetch-depth and Rebase task? Seems that the checkout
+          # without ref is doing the rebase for us.
+          # otherwise we are testing target branch instead of the PR branch (see pull_request_target trigger)
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: Rebase to current
+        run: |
+          git config user.name github-actions
+          git config user.email [email protected]
+          git log --oneline -1 origin/${{ github.event.pull_request.base.ref }}
+          git rebase origin/${{ github.event.pull_request.base.ref }}
+
+      - name: Check if all changed template files are matching master branch
+        run: |
+          changed_template_files_in_pr=$(git diff --diff-filter=M --name-only origin/${{ github.event.pull_request.base.ref }} *.yml.j2)
+          if [ -z "$changed_template_files_in_pr" ]; then
+            echo "----- No template files changed -----"
+
+            exit 0
+          fi
+
+          changed_files=$(git diff --diff-filter=M --name-only origin/master *.yml.j2)
+
+          if [ -n "$changed_files" ]; then
+            # print for debugging
+            echo "----- Template files differ with mater branch -----"
+            echo "$changed_files"
+            echo "-------------------------"
+
+            exit 1
+          fi