[BUG] git mv file directory/ creates the file directory

Hi,

When directory/ does not exist, I'd expect this to fail:

  git mv existing-file directory/

(note the trailing slash, to make it clear that directory/ is a directory). Unix's mv does fail:

  $ mv existing-file directory/
  mv: cannot move `existing-file' to `directory/': Not a directory

Instead, "git mv" seems to do the equivalent of

  git mv existing-file directory # without trailing slash