ediff-show-clashes-only

ediff-show-clashes-only is a variable defined in `ediff-merg.el'.
Its value is

nil

• Automatically becomes buffer-local when set.

Documentation:
If t, show only those diff regions where both buffers disagree with the ancestor.
This means that regions that have status prefer-A or prefer-B will be
skipped over. A value of nil means show all regions.

You can customize this variable.