Intelligent caching

[Lukas Fleischer]

On Thu, 06 Feb 2014 at 20:55:14, Jason A. Donenfeld wrote:
> This could be clever, if it's done properly. It'd have to be something
> along the lines of "this page won't ever change, unless you can create an
> sha1 hash collision", and we'd have to be certain that such pages then only
> use information out of that sha1 object, and not additional related objects
> that can be changed.
> [...]

I started to work on this. The main difficulty is that currently, the
caching layer currently sits on top of prepare_repo_cmd() and is
executed at a very early stage when there is no still no access to the
Git repository.  So before implementing this, I guess that we should
check whether the caching mechanism can be moved without performance
impacts (someone needs to review the code and benchmark this).

For now, I will just merge the patches that have been sitting in
lf/staging for several days.