[mergify] notify if no backport labels on the PRs targeting the maste…

…r branch (elastic#28022)

.backportrc.json

@@ -1,6 +1,6 @@
 {
   "upstream": "elastic/beats",
-  "branches": [ { "name": "7.x", "checked": true }, "7.15", "7.14", "7.13", "7.12" ],
+  "branches": [ { "name": "7.x", "checked": true }, "7.15", "7.14" ],
   "labels": ["backport"],
   "autoAssign": true,
   "prTitle": "Cherry-pick to {targetBranch}: {commitMessages}"

.mergify.yml

@@ -12,45 +12,6 @@ pull_request_rules:
         labels:
           - "backport"
         title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
-  - name: backport patches to 7.x branch
-    conditions:
-      - merged
-      - label=backport-v7.16.0
-    actions:
-      backport:
-        assignees:
-          - "{{ author }}"
-        branches:
-          - "7.x"
-        labels:
-          - "backport"
-        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
-  - name: backport patches to 7.13 branch
-    conditions:
-      - merged
-      - label=backport-v7.13.0
-    actions:
-      backport:
-        assignees:
-          - "{{ author }}"
-        branches:
-          - "7.13"
-        labels:
-          - "backport"
-        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
-  - name: backport patches to 7.12 branch
-    conditions:
-      - merged
-      - label=backport-v7.12.0
-    actions:
-      backport:
-        assignees:
-          - "{{ author }}"
-        branches:
-          - "7.12"
-        labels:
-          - "backport"
-        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
   - name: ask to resolve conflict
     conditions:
       - conflict
@@ -106,19 +67,6 @@ pull_request_rules:
         - files~=^\.go-version$
     actions:
       delete_head_branch:
-  - name: backport patches to 7.14 branch
-    conditions:
-      - merged
-      - label=backport-v7.14.0
-    actions:
-      backport:
-        assignees:
-          - "{{ author }}"
-        branches:
-          - "7.14"
-        labels:
-          - "backport"
-        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
   - name: automatic approval for mergify pull requests with changes in bump-rules
     conditions:
       - author=mergify[bot]
@@ -151,6 +99,48 @@ pull_request_rules:
         - files~=^\.mergify\.yml$
     actions:
       delete_head_branch:
+  - name: notify the backport policy
+    conditions:
+      - -label~=^backport
+      - base=master
+    actions:
+      comment:
+        message: |
+          This pull request does not have a backport label. Could you fix it @{{author}}? 🙏
+          To fixup this pull request, you need to add the backport labels for the needed
+          branches, such as:
+          * `backport-v./d./d./d` is the label to automatically backport to the `7./d` branch. `/d` is the digit
+
+          **NOTE**: `backport-skip` has been added to this pull request.
+      label:
+        add:
+          - backport-skip
+  - name: backport patches to 7.x branch
+    conditions:
+      - merged
+      - label=backport-v7.16.0
+    actions:
+      backport:
+        assignees:
+          - "{{ author }}"
+        branches:
+          - "7.x"
+        labels:
+          - "backport"
+        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
+  - name: backport patches to 7.14 branch
+    conditions:
+      - merged
+      - label=backport-v7.14.0
+    actions:
+      backport:
+        assignees:
+          - "{{ author }}"
+        branches:
+          - "7.14"
+        labels:
+          - "backport"
+        title: "[{{ destination_branch }}](backport #{{ number }}) {{ title }}"
   - name: backport patches to 7.15 branch
     conditions:
       - merged