make check-labels a github action workflow

.github/workflows/check-labels.yml

@@ -0,0 +1,16 @@
+name: Check labels
+
+on:
+  pull_request:
+    types: [labeled, opened, synchronize, unlabeled]
+
+jobs:
+  check-labels:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Check labels
+        run: bash ${{ github.workspace }}/.maintain/github/check_labels.sh
+        env:
+          GITHUB_PR: ${{ github.event.pull_request.number }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.gitlab-ci.yml

@@ -687,14 +687,3 @@ validator 4 4:
   <<:                              *validator-deploy
   script:
     - ./.maintain/flamingfir-deploy.sh flamingfir-validator4
-
-#### stage:                        .post
-
-check-labels:
-  stage:                           .post
-  image:                           paritytech/tools:latest
-  <<:                              *kubernetes-build
-  rules:
-    - if: $CI_COMMIT_REF_NAME =~ /^[0-9]+$/                         # PRs
-  script:
-    - ./.maintain/gitlab/check_labels.sh

.maintain/gitlab/check_labels.sh → .maintain/github/check_labels.sh

@@ -3,9 +3,12 @@
 #shellcheck source=../common/lib.sh
 source "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/../common/lib.sh"
 
+repo="$GITHUB_REPOSITORY"
+pr="$GITHUB_PR"
+
 ensure_labels() {
   for label in "$@"; do
-    if has_label 'paritytech/substrate' "$CI_COMMIT_BRANCH" "$label"; then
+    if has_label "$repo" "$pr" "$label"; then
       return 0
     fi
   done
@@ -27,15 +30,15 @@ criticality_labels=(
   'C9-critical'
 )
 
-echo "[+] Checking release notes (B) labels for $CI_COMMIT_BRANCH"
+echo "[+] Checking release notes (B) labels"
 if ensure_labels "${releasenotes_labels[@]}";  then
   echo "[+] Release notes label detected. All is well."
 else
   echo "[!] Release notes label not detected. Please add one of: ${releasenotes_labels[*]}"
   exit 1
 fi
 
-echo "[+] Checking release criticality (C) labels for $CI_COMMIT_BRANCH"
+echo "[+] Checking release criticality (C) labels"
 if ensure_labels "${criticality_labels[@]}";  then
   echo "[+] Release criticality label detected. All is well."
 else