Update Repos.stat() so that it works for the top-level
Update Repos.stat() so that it works for the top-level

In order to handle the top-level correctly, Repos.stat() needs to
handle an empty path as a special case.  Otherwise the ls-tree call
simply returns a list of blobs/trees contained in the top-level rather
than information about the top-level itself.

slonopotamus/git_svn_server