is a variable defined in `
Its value is
- Automatically becomes buffer-local when set.
If t, show only the regions that have not been changed by the user.
A region is considered to have been changed if it is different from the current
default (`default-A', `default-B', `combined') and it hasn't been marked as
`prefer-A' or `prefer-B'.
A region is considered to have been changed also when it is marked as
as `prefer-A', but is different from the corresponding difference region in
Buffer A or if it is marked as `prefer-B' and is different from the region in
You can customize this variable.