handle GitLab metadata with git

A feature request for ability to manage GitLab metadata with git pull and fast forward git merge. Metadata like:

• projects
• issues
• milestones
• comments to issues
• comments to particular commits

This could eventually define a strict schema and serve as a cross applications exchange format.

Use case:

• having git level access to those metadata we can easily automate whole process
• that would allow to have a local clone of GitLab.com hosted project at its current stage, even just read-only mirror would still be valuable
• having more read-only mirrors could help to reduce CI overload on GitLab.com by moving some to local mirror.
• access to all project information during eventual platform downtime.