URLs that start with '/' are being mistreated.
When I write a link like:
Failed job [#xxxx](/gitlab-org/gitlab-ce/issues/40837).
The URL is meant to be computed relative the server, but is being "joined" to the current URL (this issue).
This is an example.
Since when a CI job fails this is actually how the URL is generated, we should do one of:
- generate the absolute URL with nethost.
- fix the MD processor to treat these URLs as relative to the nethost.