Which is the best way to preserve files downloaded by install-tl (e.g. install-tl-20140417) to skip their download the next time install-tl is invoked and told to download from a mirror (this might include invokation with a command line argument, linking directories, etc.)? It would be nice if different versions of packages are preserved (very similar to the apt cache). I don't care about the space used/wasted by old versions on the local system, but about the internet traffic. The download of newest versions of the packages should occur automatically during installation though.
EDIT 2: http://www.tug.org/texlive/doc/install-tl.html doesn't say anything about storage of downloaded binaries. I assume they are moved from
/tmp/xzy/ to the installation destination as they are. One option might be using
-in-place from the SVN repository.
EDIT 1: Currently the invokation of
--help is buggy (at least in my case after a failed previous installation). I reported this to firstname.lastname@example.org (see http://tug.org/pipermail/tex-live/2014-May/035206.html).