Nick Oliver (PixnBits) reports in a comment on GitHub to the commit
73249eeac564567f86d8e7d70cf85efa5e5f0b5b that the file link for GitLab version 4.2 is wrong.
wrong : [GitLab URL][Hash]/tree/[File path]
correct: [GitLab URL]tree/[Hash]/[File path]
It is unclear if the current format is completely wrong or if some GitLab version really needs this.