The diff for this commit is a good illustration of what changed
in ls-tree behaviour.

 - With -r, tree nodes themselves are not shown anymore, but
   blobs in subtrees are shown.

 - The order of paths parameters do not matter, since they are
   not like arguments to /bin/ls, but are filter patterns.

 - When filter patterns overlap, unintuitive things happen.
Signed-off-by: NJunio C Hamano <junkio@cox.net>