Traditional Unix diff3 generates an ed script without the
trailing `w' and and `q' commands that save the changes.
System V diff3 generates these extra commands. GNU diff3
normally behaves like traditional Unix diff3, but with the
`-i' option it behaves like System V diff3 and appends the
`w' and `q' commands.
The `-i' option requires one of the ed script options
`-AeExX3', and is incompatible with the merged output option
`-m'.