Support alternate document root directory
This will be useful for supporting no-downtime upgrades. Admins attempting to upgrade GitLab via our no-downtime upgrade procedure have found that CSS and JavaScript often don't load while the upgrade is in progress. This is because in a mixed deployment scenario with a load balancer, this can happen:
- User accesses node version N+1, which then makes a CSS/JS request on version N.
- User accesses node version N, which then makes a CSS/JS requests on version N+1.
In both scenarios, the user gets a 404 since only one version of the assets exist on a given server.
To fix this, we provide an alternate path where previous and future assets can be stored.
Relates to #304 (moved)
Edited by Stan Hu