Add automerge feature

.gitlab-ci.yml

+stages:
+   - prepare
+   - trigger
+
+
+automerge:
+   image: busybox
+   stage: prepare
+   script:
+      - echo "Success"
+   except:
+      changes:
+         - .gitlab-ci.yml
+
+
 trigger build:
+    stage: trigger
     image: python:alpine
     variables:
         GIT_CLONE_STRATEGY: none