diff can produce output that is like an ed script, but with hunks in forward (front to back) order. The format of the commands is also changed slightly: command characters precede the lines they modify, spaces separate line numbers in ranges, and no attempt is made to disambiguate hunk lines consisting of a single period. Like ed format, forward ed format cannot represent incomplete lines.
Forward ed format is not very useful, because neither ed nor patch can apply diffs in this format. It exists mainly for compatibility with older versions of diff. Use the -f or --forward-ed option to select it.