feat(git_push_mirror): ability to disable job with variable

!21

git_push_mirror/.gitlab-ci.yml

@@ -6,6 +6,7 @@
         - apk update
         - apk add git
     script:
+        - if [ "0$GIT_SYNC_URL" == "0"]; then echo "[ERROR] you must define variable GIT_SYNC_URL for mirroring this repository."; fi
         - git clone https://gitlab-ci-token:${CI_JOB_TOKEN}@gitlab.com/$CI_PROJECT_PATH --mirror $CI_PROJECT_NAME
         - cd $CI_PROJECT_NAME 
         - git remote add destination $GIT_SYNC_URL 
@@ -14,7 +15,9 @@
     artifacts:
         expire_in: 1 day
     rules:
-        - if: '$CI_COMMIT_BRANCH == "master"'
-        - if: '$CI_COMMIT_BRANCH == "development"'
+        - if: '$JOB_STOP_GIT_PUSH_MIRROR'
+          when: never
+        - if: '$CI_COMMIT_BRANCH == "master" && $GIT_SYNC_URL != null'
+        - if: '$CI_COMMIT_BRANCH == "development" && $GIT_SYNC_URL != null'
           when: always