GitLab and omnibus do not process component version files in the same way

Omnibus considers the content of component version file (i.e. GITALY_SERVER_VERSION) as an absolute git reference. relevant code

But the GitLab rake file to prepare tests requires the component version file to start with = to be an absolute git reference.

If not it will prepend v to the cloning operation. relevant code

The problem is that tagging a release will copy the content of component version files from GitLab to omnibus, on they are not compatible.

This blocked the first attempt to auto-deploy gitaly gitlab-com/gl-infra/delivery#516 (comment 235026684)