The reader machinery will be extended to handle conditional includes.
The only conditions that currently exist all match the against the git
directory of the repository the config file belongs to. As such, we need
to have access to the repository when reading configuration files to
properly handle these conditions.

One specialty of thes conditional includes is that the actual pattern
may also be a relative pattern starting with "./". In this case, we have
to match the pattern against the path relative to the config file which
is currently being parsed. So besides the repository, we also have to
pass down the path to the current config file that is being parsed.