Traditional Unix diff3 generates an ed script without the
trailing ‘w’ 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.