#!/bin/bash

sed -e '

# fix incorrect sig delimiters

s/^--$/-- /

# and those who put name on same line as delimiter, eg:
# -- John Smith

s/^-- \(.*\)/-- \
\1/

# put a space before sig delimiters

#/^-- /{g;s/^$/-- /;t;s/.*/\n-- /};h

'