[CI] Add GitHub action for fixing version label gaps (#106467)

.github/workflows/backport.yml

@@ -28,6 +28,11 @@ jobs:
       - name: Install Actions
         run: npm install --production --prefix ./actions
 
+      - name: Fix Version Label Gaps
+        uses: ./actions/fix-version-gaps
+        with:
+          github_token: ${{secrets.KIBANAMACHINE_TOKEN}}
+
       - name: Run Backport
         uses: ./actions/backport
         with:

.github/workflows/fix-version-gaps.yml

@@ -0,0 +1,35 @@
+on:
+  pull_request:
+    branches:
+      - master
+    types:
+      - closed
+
+jobs:
+  gaps:
+    name: Fix Version Label Gaps
+    # This fix also runs as part of the backport action (because backport depends on the labels)
+    # So we only need to trigger it for merged PRs that also won't be auto-backported
+    if: |
+      github.event.pull_request.merged == true
+      && !contains(github.event.pull_request.labels.*.name, 'auto-backport')
+      && !(
+        (github.event.action == 'labeled' && github.event.label.name == 'auto-backport')
+        || (github.event.action == 'closed')
+      )
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Actions
+        uses: actions/checkout@v2
+        with:
+          repository: 'elastic/kibana-github-actions'
+          ref: main
+          path: ./actions
+
+      - name: Install Actions
+        run: npm install --production --prefix ./actions
+
+      - name: Run Fix Gaps
+        uses: ./actions/fix-version-gaps
+        with:
+          github_token: ${{secrets.KIBANAMACHINE_TOKEN}}