Relative links in Markdown files in branches [6.5.1]

Created by: thewholelifetolearn

My issue is similar to #3556 (closed) and #5044 (closed) .

The links between Markdown files when they are relative works but only in the master branch. When you go through a branch, the links refer to the wiki.

I' have upgraded GitLab from v6.1.0 to v6.5.1, one major version at a time this morning. I don't know if in 6.2., 6.3. and 6.4.* the issue is encountered too as I didn't do full tests. @vagari mentions in https://github.com/gitlabhq/gitlabhq/issues/3556#issuecomment-32286310 that the links do work in 6.4 .

It would be great if it works right again. In any case, thanks to all developers that contribute to GitLab.