title: Merge request dropped from merge train with "No stages / jobs for this pipeline."
body: <p>When I click <kbd>Start merge train</kbd> on a merge request (MR), GitLab adds the following to the MR's system notes:</p>
  
  <blockquote>
    <p>@sferencik started a merge train just now</p>
  </blockquote>
  
  <p>Great. However, seconds later the following is added to the system notes:</p>
  
  <blockquote>
    <p>@sferencik removed this merge request from the merge train because <strong>No stages / jobs for this pipeline.</strong> just now</p>
  </blockquote>
  
  <p>[emphasis mine]</p>
  
  <p>The list of pipelines doesn't have a new entry: the merge train didn't even get as far as starting one.</p>
  
  <p>The <a href="https://docs.gitlab.com/ee/ci/merge_request_pipelines/pipelines_for_merged_results/merge_trains/#merge-request-dropped-from-the-merge-train-immediately" rel="noreferrer">GitLab documentation</a> touches on this. <a href="https://gitlab.com/gitlab-org/gitlab-ee/issues/12118" rel="noreferrer">This GitLab issue</a> also talks about this, though in a different context.</p>
  
  <p>What am I doing wrong? I have cut down my <code>.gitlab-ci.yml</code> to the bare minimum, leaving only one stage with one job, which is not <a href="https://docs.gitlab.com/ee/ci/yaml/#onlyexcept-basic" rel="noreferrer">conditional</a>. It beats me why GitLab, having performed the <a href="https://docs.gitlab.com/ee/ci/merge_request_pipelines/pipelines_for_merged_results/index.html" rel="noreferrer">speculative merge</a>, should create a pipeline with "no stages / jobs."</p>
  
  <p>This is <em>not</em> a build issue: by the time I click <kbd>Start merge train</kbd>, a pipeline has succeeded on my feature branch (the one I want to merge).</p>
  
  <p>Also, if I switch off <a href="https://docs.gitlab.com/ee/ci/merge_request_pipelines/pipelines_for_merged_results/index.html#enabling-pipelines-for-merged-results" rel="noreferrer">pipelines for merge results</a>, my MRs have a <kbd>Merge</kbd> button instead of <kbd>Start merge train</kbd> and it works just fine.</p>
  
  <p>This started happening with our upgrade from GitLab 12.0 to 12.1.</p>