Only changes do not run after merge.

Summary

We are trying to speed up our CI by leveraging only/changes on prepare/test jobs. It helps on feature branches but after merge it skips all those jobs which causes bundling and build fail because of missing node_modules and also skipping the tests on merged code.

Steps to reproduce

(How one can reproduce the issue - this is very important)

Example Project

test-libs:
  tags: ['docker']
  stage: test
  image: node:10-slim
  services:
    - name: nats-streaming
      alias: nats
    - name: dwmkerr/dynamodb
      alias: dynamodb
  script:
    - yarn ci:libs
  dependencies:
    - install
  only:
    changes:
      - lib/**/*
      - yarn.lock

install:
  tags: ['docker']
  stage: prepare
  cache:
    untracked: true
    key: '$CI_BUILD_REF_NAME'
  script:
    - yarn install
  artifacts:
    untracked: true
  only:
    changes:
      - lib/**/*
      - driver/**/*
      - service/**/*
      - api/**/*
      - yarn.lock
      - package.json

What is the current bug behavior?

install will not run on develop after merge request even if this MR introduced changes in mentioned paths. test-libs will not run on develop after merge even if yarn.lock has changed.

What is the expected correct behavior?

Changes introduced by MR should run those jobs.

Results of GitLab environment info

Latest version of Gitlab.