[DRE-maint] Bug#820505: wiki fails to create

[TheSin]

Okay I got it working, I copied it form upstream

/usr/share/gitlab/app/models/project_wiki.rb

Change

["/", @project.path_with_namespace, "/wikis"].join('')
To
[Gitlab.config.gitlab.relative_url_root, "/", @project.path_with_namespace, "/wikis"].join('')

And

rescue Gollum::NoSuchPathError
To
rescue Rugged::OSError

restart gitlab and bang, new projects have a working wiki when created.  I didn’t try forks, or if old project magically got them, but this will work for new at the very least.  Hope it helps.