* master: (363 commits)
  Added changelog item for issuable form dropdowns
  Add 'run tests' docs from GDK
  Bump gitlab_git to lazy load compare commits
  Add examples to repository files API (!5465)
  Ignore URLs starting with // (!5677)
  Add failing test for #7032
  Update timeago to shorter representation
  Add missing DOWNTIME constant to the AddTimestampsToMembersAgain migration
  Added guide about migrations and downtime
  Update CHANGELOG for 8.10.4
  Add a data migration to fix some missing timestamps in the members table (again)
  Move abilities by subject class to a dedicated method
  Remove unnecessary empty line after css var
  Set consistency in list text height css
  Add description to text/plain emails
  Fix Rename `add_users_into_project` and `projects_ids`
  fix spec
  Underscore variable to camelCase
  using shared path for project import uploads and refactored gitlab remove export worker
  Structure the development documentation
  ...