ci: enable backport for v0.8 and v0.7 (#784)

* ci: enable backport for v0.8 and v0.7

* changelog

.mergify.yml

@@ -1,10 +1,34 @@
+queue_rules:
+  - name: default
+    conditions:
+      - "#approved-reviews-by>1"
+
 pull_request_rules:
-  - name: automerge to base branch with label automerge and branch protection passing
+  - name: automerge to the base branch with label automerge and branch protection passing
     conditions:
       - "#approved-reviews-by>1"
       - base=main
       - label=automerge
     actions:
+      queue:
+        name: default
       merge:
         method: squash
         strict: true
+        commit_message: title+body
+  - name: backport patches to v0.8.x branch
+    conditions:
+      - base=main
+      - label=backport/0.8.x
+    actions:
+      backport:
+        branches:
+          - release/v0.8.x
+  - name: backport patches to v0.7.x branch
+    conditions:
+      - base=main
+      - label=backport/0.7.x
+    actions:
+      backport:
+        branches:
+          - release/v0.7.x

CHANGELOG.md

@@ -37,6 +37,10 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## Unreleased
 
+## Improvements
+
+* (ci) [tharsis#784](https://github.com/tharsis/ethermint/pull/784) Enable automatic backport of PRs.
+
 ### Bug Fixes
 
 * (feemarket) [tharsis#770](https://github.com/tharsis/ethermint/pull/770) Enable fee market (EIP1559) by default.