title: Issue with gitlab's continuous integration with submodules
body: <p>I have a several projects that use a common project as a submodule.
  The submodule is hosted on gitlab as well, but it is a different project under a different base name.</p>
  
  <p>In each project, the submodule is linked using a git address and not a relative path.</p>
  
  <p>CI builds constantly fail because they claim they don’t have the permissions to pull the submodule.</p>
  
  <p>How can I pass credentials for a submodule in CI? since it’s the same user account, why are credentials even needed?</p>
  
  <p>I get an error like this:</p>
  
  <blockquote>
    <p>MSBUILD : error MSB1003: Specify a project or solution file. The current working directory does not contain a project or solution file.
    section_end:1558348623:build_scriptsection_start:1558348623:after_scriptsection_end:1558348625:after_scriptsection_start:1558348625:upload_artifacts_on_failuresection_end:1558348627:upload_artifacts_on_failureERROR: Job failed: exit code 1</p>
  </blockquote>
  
  <p>But after investigation, it's always because the submodule is not pulled.</p>