environment variables to configure paths

Hi,
i'm packaging redmine for debian, and i thought it would be nice
to make config paths settable by environment variables, like those :
config.log_path
config.cache_store
config.database_configuration_file
ActionController::Base.session_options[:tmpdir]

instead of having to patch or ask upstream any future webapp,
it would be so nice to configure those variables (or any other
typically
configurable path) through environment variables like
RAILS_LOG
RAILS_CACHE
RAILS_ETC
RAILS_SESSION
that's only a proposition.

I don't really feel that this would be a suitable way of defaulting
those settings within rails itself. However you could override them
in an initializer yourself which wouldn't require a patch, merely a
new file included in the distribution.