WIP: POC for releases to be done by the CI

Todo:

• The runner will need right to push to all the gitlab-ce, gitlab-ee and omnibus-gitlab remotes
• Decide on the tag naming:
  • gitlab-ee+ce-8.6.3 would release 8.6.3 for both EE and CE
  • gitlab-ee-8.6.3 would release 8.6.3 for EE only
  • gitlab-ce-8.6.3 would release 8.6.3 for CE only
• Test this? How?

Fixes #17.

Added 1 commit:

• f773df10 - Add Git user config and refactor jobs