I actually use `repo_file` in the ESXi installer, since I need to rewrite some files (eg: boot.cfg) from the ESXi repository on the fly, ugly as that is.  (The alternative is to hard-code their list of "things the installer needs" into our code, which may well break if they ship 5.5.1 with one extra file need or something.  That seemed worse...)

I will check and see if it can be reused here, but the real purpose of that method was exposing it to the templates so they can get the path to a file inside the repo in a portable, supported fashion.