branch.<name>.remote can be set to '.' (period) as the repository
path (URL) as part of the remote name dwimmery. Tell the reader.
Such relative paths are not 'special'. Correct the branch.<name>.merge
note.
Signed-off-by: Philip Oakley <philipoakley@iee.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>