Provide clarification on mirrored repositories for pipelines (!18105) · Merge requests · GitLab.org / GitLab FOSS · GitLab

Achilleas Pipinellis - OOO until November 25th (parental leave) requested to merge docs/mirrored-repositories-for-pipelines-ce into master Mar 30, 2018

What does this MR do?

Port of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5125