We need a way to calculate space taken by certain files.

Use cases: I want to drop some files from my small disk. I need to figure out things that take most space, and drop them.

Usage examples:

    git annex du -hs *.mp3
    git annex du -sBm --in=here *.ogg

Would be nice if it was compatible with standard unix `df`.

> `du -L` works.
> 
> See also: [[forum/Wishlist:_getting_the_disk_used_by_a_subtree_of_files]]