added github action to add a hold label when PRs are pushed to branch other than main (#1570)

Signed-off-by: Nir Rozenbaum <[email protected]>

Author: nirrozenbaum

.github/workflows/non-main-gatekeeper.yml

@@ -0,0 +1,18 @@
+name: Label non-main PRs
+
+on:
+  pull_request:
+    types: [opened, edited, synchronize, reopened]
+
+jobs:
+  add-label:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Add labels when base branch is not main
+        if: github.event.pull_request.base.ref != 'main'
+        uses: actions-ecosystem/action-add-labels@v1
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          labels: |
+            do-not-merge/hold
+            do-not-merge/cherry-pick-not-approved