Merge branch 'master' into feature/improve-mrwbs-and-todos-for-pipelines

* master: (221 commits)
  Add CHANGELOG entry for 8.12.6
  Added 'Download' button to snippet view
  Merge branch 'api-fix-project-group-sharing' into 'security'
  Add 8.12.5, 8.11.9, and 8.10.12 CHANGELOG entries
  FIx JS bug with select2 because of missing `data-field` attribute in select box.
  Remove pointless `.vagrant_enabled` file
  allow multiple labels commands
  Move some CHANGELOG entries to the 8.13.0 part
  Move operations/ to new location
  Move health check docs under user/admin_area/monitoring
  Make guests unable to view MRs
  Add examples of fake tokens to be used in docs
  Remove duplicate CHANGELOG entry
  Allow browsing branches that end with '.atom'
  Refactor the SubGit/SVN documentation
  Document the new CI_DEBUG_TRACE variable
  Remove redundant images
  changed the scss for the top line connectors to be exactly centered
  Rearrange GitLab basics READMEs
  New images for GitLab basics "Create MR" docs
  ...

Conflicts:
  app/models/commit_status.rb