ci: add release freeze gate (#11621)

.github/workflows/prepare-release.yml

@@ -25,6 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     permissions:
+      actions: write
       contents: write
       pull-requests: write
     steps:
@@ -33,6 +34,12 @@ jobs:
       with:
         egress-policy: audit
 
+    - name: Enable release freeze
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        gh variable set RELEASE_FREEZE --body true --repo "${GITHUB_REPOSITORY}"
+
     - name: Checkout repository
       uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with:

.github/workflows/release-freeze-gate.yml

@@ -0,0 +1,40 @@
+name: 'Tools: Release Freeze Gate'
+
+on:
+  pull_request:
+    branches:
+      - 'master'
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - ready_for_review
+  merge_group:
+    branches:
+      - 'master'
+    types:
+      - checks_requested
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  release-freeze-gate:
+    name: release-freeze-gate
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Check release freeze status
+        env:
+          RELEASE_FREEZE: ${{ vars.RELEASE_FREEZE }}
+        run: |
+          case "${RELEASE_FREEZE}" in
+            true|TRUE|True)
+              echo "::error::Release freeze is active. Merges to master are temporarily blocked."
+              echo "Set the RELEASE_FREEZE repository variable to false when the release is complete."
+              exit 1
+              ;;
+            *)
+              echo "Release freeze is not active."
+              ;;
+          esac